Hand-held dual spherical antenna system

ABSTRACT

A hand-held antenna system allows medical personnel to ascertain the presence or absence of objects (e.g., medical supplies) tagged with transponders in an environment in which medical procedures are performed. In use, the hand-held antenna system may be positioned proximate a patient at a time after a medical procedure, such as after childbirth, so the system can scan the patient&#39;s body to determine the presence of objects tagged with transponders. The antenna system includes two sets of three antenna elements arranged mutually orthogonal to each other to transmit and receive signals in at least three coordinate directions. A controller is coupled to the antenna elements to transmit signals to the transponders and to receive response signals. The antenna system may operate in a static scan mode wherein the antenna system is held in a fixed position by a user and a dynamic scan mode wherein the antenna system is moved by a user.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/127,130 filed Mar. 2, 2015, the entiredisclosure of which is incorporated by reference herein.

BACKGROUND

1. Field

This disclosure generally relates to the detection of the presence orabsence of objects tagged with transponders, which may, for example,allow the detection of retained medical supplies during medicalprocedures.

2. Description of the Related Art

It is often useful or important to be able to determine the presence orabsence of an object.

For example, it is important to determine whether objects associatedwith surgery are present in a patient's body before completion of thesurgery. Such objects may take a variety of forms. For example, theobjects may take the form of instruments, for instance scalpels,scissors, forceps, hemostats, and/or clamps. Also for example, theobjects may take the form of related accessories and/or disposableobjects, for instance surgical sponges, gauzes, and/or pads. Failure tolocate an object before closing the patient may require additionalsurgery, and in some instances may have serious adverse medicalconsequences.

Some hospitals have instituted procedures which include checklists orrequiring multiple counts to be performed to track the use and return ofobjects during surgery. Such a manual approach is inefficient, requiringthe time of highly trained personnel, and is prone to error.

Another approach employs transponders and a wireless interrogation anddetection system. Such an approach employs wireless transponders whichare attached to various objects used during surgery. The interrogationand detection system includes a transmitter that emits pulsed widebandwireless signals (e.g., radio or microwave frequency) and a detector fordetecting wireless signals returned by the transponders in response tothe emitted pulsed wideband signals. Such an automated system mayadvantageously increase accuracy while reducing the amount of timerequired of highly trained and highly compensated personnel. Examples ofsuch an approach are discussed in U.S. Pat. No. 6,026,818, issued Feb.22, 2000, and U.S. Patent Publication No. US 2004/0250819, publishedDec. 16, 2004.

Commercial implementation of such an automated system requires that theoverall system be cost competitive and highly accurate. In particular,false negatives must be avoided to ensure that objects are notmistakenly left in the patient. Some facilities may wish to install asingle interrogation and detection system in each surgery theater, whileother facilities may move an interrogation and detection system betweenmultiple surgical theaters. In either case, the overall system willrequire a large number of transponders, since at least one transponderis carried, attached or otherwise coupled to each object which may orwill be used in surgery. Consequently, the transponders must beinexpensive. However, inexpensive transponders typically have arelatively large variation in the frequency of signals they emit, makingit difficult to accurately detect the signals returned by thetransponders. This may be particularly difficult in some environmentswhich are noisy with respect to the particular resonant frequencies ofthe transponders. Consequently, a new approach to detection of thepresence and absence of transponder that facilitates the use ofinexpensive transponders is highly desirable.

BRIEF SUMMARY

A transponder detection device to detect surgical objects in a workarea, the surgical objects marked by respective resonant tag elementsthat produce return signals in response to energization, may besummarized as including a hand-held probe comprising: a housing having acavity therein; and a first coil assembly and a second coil assemblyreceived within the cavity of the housing spaced from each other,wherein each of the first and the second coil assemblies respectivelyincludes: a substantially spherically shaped coil form that includesthree coil support channels, each of the three coil support channelswhich define an outer coil support surface; a first antenna elementcomprising a first electrical conductor wound around the outer coilsupport surface of a first one of the three coil support channels, thefirst antenna element arranged to transmit and receive signals generallyin a first coordinate direction; a second antenna element comprising asecond electrical conductor wound around the outer coil support surfaceof a second one of the three coil support channels over the firstelectrical conductor, the second antenna element arranged to transmitand receive signals generally in a second coordinate directionorthogonal to the first coordinate direction; and a third antennaelement comprising a third electrical conductor wound around the outercoil support surface of a third one of the three coil support channelsover the first electrical conductor and the second electrical conductor,the third antenna element arranged to transmit and receive signalsgenerally in a third coordinate direction orthogonal to the firstcoordinate direction and the second coordinate direction. The cavity ofthe housing may be defined by a first body portion that receives thefirst coil assembly, a second body portion that receives the second coilassembly, and a handle portion disposed between the first body portionand the second body portion. The handle portion may be disposed betweenthe first body portion and the second body portion to allow the firstbody portion and the second body portion to at least partially surrounda human joint during use.

The handle portion may include a handle portion cavity, and thehand-held probe may further include a circuit board disposed within thehandle portion cavity and electrically coupled to the respective firstantenna elements, the second antenna elements and the third antennaelements of the first and the second coil assemblies. At least one ofthe first, the second or the third antenna elements of the first coilassembly may be arranged to transmit and receive signals generally in acoordinate direction which is the same as a coordinate direction inwhich at least one of the first, the second or the third antennaelements of the second coil assembly is arranged to transmit and receivesignals. Each of the first, the second and the third antenna elements ofthe first coil assembly may be arranged to transmit and receive signalsgenerally in a coordinate direction which is the same as a coordinatedirection in which a different one of the first, the second or the thirdantenna elements of the second coil assembly is arranged to transmit andreceive signals. At least one of the first, the second or the thirdantenna elements of the first coil assembly may be coplanar with atleast one of the first, the second or the third antenna elements of thesecond coil assembly. For each of the respective coil forms of the firstand the second coil assemblies, each of the three coil support channelsmay be shaped as a spherical zone of a virtual sphere. For each of therespective coil forms of the first and the second coil assemblies, eachof the three coil support channels may be shaped as a spherical zone ofa virtual sphere centered on a great circle of the virtual sphere. Foreach of the respective coil forms of the first and the second coilassemblies, the three coil support channels may be shaped as a sphericalzone of the substantially spherically shaped coil form centered onrespective orthogonal great circles of the coil form.

The transponder detection device may further include a light sourcecoupled to the housing that provides a visual indication of at least astatus of the transponder detection device.

The transponder detection device may further include a processoroperatively coupled to the respective first antenna elements, the secondantenna elements, and the third antenna elements of the first and thesecond coil assemblies; and a nontransitory processor-readable mediumcommunicatively coupled to the processor and that stores at least one ofinstructions or data executable by the processor, which cause theprocessor to: control each of the first antenna elements, the secondantenna elements and the third antenna elements of the first and thesecond coil assemblies to emit wideband interrogation signals; receiveany of the return signals from any of the resonant tag elements; anddetermine from a receipt of any of the return signals whether any of theresonant tag elements are present in the work area. The processor maycontrol each of the respective first antenna elements, the secondantenna elements and the third antenna elements of the first and thesecond coil assemblies to emit wideband interrogation signals intime-wise succession during a transmit portion of respective transmitand receive cycles, and controls each of the first antenna elements, thesecond antenna elements and the third antenna elements of the first andthe second coil assemblies to not emit wideband interrogation signalsduring a receive portion of respective transmit and receive cycles. Theprocessor may receive any of the return signals from any of the resonanttag elements during a receive portion of respective transmit and receivecycles. The processor may filter the any received return signals fromnoise to determine whether any of the resonant tag elements are presentin the work area.

The processor may further receive a selection of at least one of adynamic scan mode and a static scan mode; in response to receiving aselection of the static scan mode, may control each of the first antennaelements, the second antenna elements and the third antenna elements toemit wideband interrogation signals according to a static instrumentscan cycle having a static instrument scan cycle duration; and inresponse to receiving a selection of the dynamic scan mode, may controleach of the first antenna elements, the second antenna elements and thethird antenna elements to emit wideband interrogation signals accordingto a dynamic instrument scan cycle having a dynamic instrument scancycle duration that is less than the static instrument scan cycleduration. Tn response to receiving a selection of the static scan mode,the processor may control each of the first antenna elements, the secondantenna elements and the third antenna elements to emit widebandinterrogation signals centered on a first frequency, and furthercontrols each of the first antenna elements, the second antenna elementsand the third antenna elements to emit wideband interrogation signalscentered on a second frequency, the second frequency different from thefirst frequency. The static instrument scan cycle duration may be lessthan fifteen (15) seconds and the dynamic instrument scan cycle durationmb less than five (5) seconds.

The processor may further determine from a receipt of any of the returnsignals whether any of the resonant tag elements are present in the workarea based at least in part on a frequency of the return signalsreceived being within a defined frequency range. The defined frequencyrange may include the frequency range of about 137 kHz to about 160 kHz.

The processor may further determine whether any of the resonant tagelements are present in the work area based at least in part on a Qvalue of the return signals received.

The processor may further determine whether any of the resonant tagelements are present in the work area based at least in part on a Qvalue of the return signals received being at least equal to a thresholdQ value. The threshold Q value may be 35.

The processor may further determine whether any of the resonant tagelements are present in the work area based at least in part on a signaldetection threshold. The processor may further receive electromagneticsignals during a noise detection portion; determine a noise valueindicative of a noise level that corresponds to a number of measurementsof the electromagnetic signals received during the noise detectionportion; adjust a signal detection threshold based at least in part onthe determined noise value; and determine whether any of the resonanttag elements are present in the work area based at least in part on anumber of measurements of the return signals received and the adjustedsignal detection threshold.

The processor may further compare a maximum value of a plurality ofmatched filter outputs with the adjusted signal detection threshold.

The processor may further adjust the signal detection threshold to beapproximately twice the determined noise value.

The processor may further determine if an output of at least one matchedfilter during the noise detection portion exceeds a noise faultthreshold indicative of a noise fault. The wideband interrogationsignals may be centered in at least one of a 136 kHz band, a 139 kHzband, a 142 kHz band, a 145 kHz band, a 148 kHz band, a 151 kHz band ora 154 kHz band.

A method to detect surgical objects in a work area, the surgical objectsmarked by respective resonant tag elements that produce return signalsin response to energization, may be summarized as including providing atransponder detection device that includes a hand-held probe comprisinga housing having a cavity therein; a first coil assembly and a secondcoil assembly received within the cavity of the housing spaced from eachother, wherein each of the first and the second coil assembliesrespectively includes: a substantially spherically shaped coil form thatincludes three coil support channels, each of the three coil supportchannels which define an outer coil support surface; a first antennaelement comprising a first electrical conductor wound around the outercoil support surface of a first one of the three coil support channels,the first antenna element arranged to transmit and receive signalsgenerally in a first coordinate direction; a second antenna elementcomprising a second electrical conductor wound around the outer coilsupport surface of a second one of the three coil support channels overthe first electrical conductor, the second antenna element arranged totransmit and receive signals generally in a second coordinate directionorthogonal to the first coordinate direction; and a third antennaelement comprising a third electrical conductor wound around the outercoil support surface of a third one of the three coil support channelsover the first electrical conductor and the second electrical conductor,the third antenna element arranged to transmit and receive signalsgenerally in a third coordinate direction orthogonal to the firstcoordinate direction and the second coordinate direction; emittingwideband interrogation signals via the respective first antennaelements, the second antenna elements and the third antenna elements ofthe first and the second coil assemblies; receiving any of the returnsignals from any of the resonant tag elements via at least one of therespective first antenna elements, the second antenna elements and thethird antenna elements of the first and the second coil assemblies; anddetermining from a receipt of any of the return signals whether any ofthe resonant tag elements are present in the work area.

The method may further include positioning the hand-held probe proximatea human body such that the first coil assembly and the second coilassembly at least partially surround a joint of the human body. Emittingwideband interrogation signals via the respective first antennaelements, the second antenna elements and the third antenna elements mayinclude, for each of the first antenna elements, the second antennaelements and the third antenna elements, emitting a first widebandinterrogation signal centered at a first frequency and emitting a secondwideband interrogation signal centered at a second frequency, the secondfrequency different from the first frequency.

The method may further include controlling each of the first antennaelements, the second antenna elements and the third antenna elements toemit wideband interrogation signals in time-wise succession during atransmit portion of respective transmit and receive cycles andcontrolling each of the first antenna elements, the second antennaelements and the third antenna elements to not emit widebandinterrogation signals during a receive portion of respective transmitand receive cycles.

The method may further include filtering the any received return signalsfrom noise to determine whether any of the resonant tag elements arepresent in the work area.

The method may further include controlling each of the first antennaelements, the second antenna elements and the third antenna elements toemit wideband interrogation signals according to a static instrumentscan cycle having a static instrument scan cycle duration; andcontrolling each of the first antenna elements, the second antennaelements and the third antenna elements to emit wideband interrogationsignals according to a dynamic instrument scan cycle having a dynamicinstrument scan cycle duration that is less than the static instrumentscan cycle duration.

The method may further include receiving a selection of at least one ofthe dynamic instrument scan cycle and the static instrument scan cyclevia the user interface.

The method may further include in response to receiving a selection ofthe static instrument scan cycle, controlling each of the first antennaelements, the second antenna elements and the third antenna elements toemit wideband interrogation signals centered on a first frequency; andcontrolling each of the first antenna elements, the second antennaelements and the third antenna elements to emit wideband interrogationsignals centered on a second frequency, the second frequency differentfrom the first frequency.

The method may further include determining from a receipt of any of thereturn signals whether any of the resonant tag elements are present inthe work area based at least in part on a frequency of the returnsignals received being within a defined frequency range.

The method may further include determining whether any of the resonanttag elements are present in the work area based at least in part on a Qvalue of the return signals received.

The method may further include determining whether any of the resonanttag elements are present in the work area based at least in part on a Qvalue of the return signals received being at least equal to a thresholdQ value.

The method may further include determining whether any of the resonanttag elements are present in the work area based at least in part on asignal detection threshold.

The method may further include receiving electromagnetic signals duringa noise detection portion; determining a noise value indicative of anoise level that corresponds to a number of measurements of theelectromagnetic signals received during the noise detection portion;adjusting a signal detection threshold based at least in part on thedetermined noise value; and determining whether any of the resonant tagelements are present in the work area based at least in part on a numberof measurements of the return signals received and the adjusted signaldetection threshold.

The method may further include comparing a maximum value of a pluralityof matched filter outputs with the adjusted signal detection threshold.

The method may further include adjusting the signal detection thresholdto be approximately twice the determined noise value.

The method may further include determining if an output of at least onematched filter during the noise detection portion exceeds a noise faultthreshold indicative of a noise fault.

A transponder detection device may be summarized as including a firstcoil assembly and a second coil assembly spaced apart from each other,wherein each of the first and the second coil assemblies respectivelyincludes: a coil form that includes three coil support channels, each ofthe coil support channels curved about a respective primary axis andcurved about a respective secondary axis orthogonal to the respectiveprimary axis, the primary axes orthogonal to one another.

The first and the second coil assemblies respectively may include afirst antenna element comprising a first electrical conductor woundaround a first one of the three coil support channels; a second antennaelement comprising a second electrical conductor wound around a secondone of the three coil support channels over the first electricalconductor; and a third antenna element comprising a third electricalconductor wound around a third one of the three coil support channelsover the first electrical conductor and the second electrical conductor.

The transponder detection device may further include a processoroperatively coupled to the respective first antenna elements, the secondantenna element and the third antenna elements of the first and thesecond coil assemblies; and a nontransitory processor-readable mediumcommunicatively coupled to the processor and that stores at least one ofinstructions or data executable by the processor, which cause theprocessor to: control each of the first antenna elements, the secondantenna elements and the third antenna elements to emit widebandinterrogation signals; receive return signals from one or more resonanttag elements; and determine from a receipt of any of the return signalswhether any of the resonant tag elements are present in a work area.Curvatures of the three coil support channels about the respectiveprimary axes may be equal to one another and equal to curvatures of thecoil support channels about the respective secondary axes.

A transponder detection device may be summarized as including at leasttwo coil forms spaced apart from each other, each of the coil formsrespectively includes: a first coil support channel curved about aprimary axis defined by a first axis and curved about a secondary axisdefined by a second axis orthogonal to the first axis; a second coilsupport channel curved about a primary axis defined by third axis andcurved about a secondary axis defined by the first axis, the third axisorthogonal to the first axis and the second axis; and a third coilsupport channel curved about a primary axis defined by the second axisand curved about a secondary axis defined by the first axis. Curvaturesof the respective first, the second, and the third coil support channelsabout the respective primary axes may be equal to one another and equalto curvatures of the respective first, the second, and the third coilsupport channels about the respective secondary axes.

The transponder detection device may further include for each of the atleast two coil forms, a first antenna element comprising a firstelectrical conductor wound around the first coil support channel; asecond antenna element comprising a second electrical conductor woundaround the second coil support channel over the first electricalconductor; and a third antenna element comprising a third electricalconductor wound around the third coil support channel over the firstelectrical conductor and the second electrical conductor.

The transponder detection device may further include a processoroperatively coupled to the respective first antenna elements, the secondantenna elements, and the third antenna elements; and a nontransitoryprocessor-readable medium communicatively coupled to the processor andthat stores at least one of instructions or data executable by theprocessor, which cause the processor to: control each of the firstantenna elements, the second antenna elements and the third antennaelements to emit wideband interrogation signals; receive return signalsfrom one or more resonant tag elements; and determine from a receipt ofany of the return signals whether any of the resonant tag elements arepresent in a work area.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not necessarily drawn to scale, and some ofthese elements may be arbitrarily enlarged and positioned to improvedrawing legibility. Further, the particular shapes of the elements asdrawn, are not necessarily intended to convey any information regardingthe actual shape of the particular elements, and may have been solelyselected for ease of recognition in the drawings.

FIG. 1A is a schematic diagram showing a surgical environmentillustrating a medical provider using an interrogation and detectionsystem to detect an object tagged with a transponder in a patient,according to one illustrated implementation.

FIG. 1B is a schematic diagram showing another surgical environmentillustrating a medical provider using the interrogation and detectionsystem to detect an object tagged with a transponder in a patient,according to one illustrated implementation.

FIG. 2A is a schematic diagram of a transponder, according to oneillustrated implementation.

FIG. 2B is a schematic diagram of a transponder, according to anotherillustrated implementation.

FIG. 2C is a schematic diagram of a transponder, according to a furtherillustrated implementation.

FIG. 2D is a side elevational view of a transponder, according to yet afurther illustrated implementation.

FIG. 2E is an end view of the transponder of FIG. 2D.

FIG. 2F is a cross-sectional view of the transponder of FIG. 2D, takenalong section line 2F.

FIG. 2G is an isometric view of a ferrite core of the transponder ofFIG. 2D.

FIG. 3A is a top front isometric view of a probe of the interrogationand detection system, according to one illustrated implementation.

FIG. 3B is a bottom rear isometric view of the probe of theinterrogation and detection system, according to one illustratedimplementation.

FIG. 3C is a right side elevational view of the probe of theinterrogation and detection system, according to one illustratedimplementation.

FIG. 3D is an isometric view of a coil form and three mutuallyorthogonal coils of the probe of FIG. 3A.

FIG. 4 is an isometric view of a controller of the interrogation anddetection system, according to one illustrated implementation.

FIG. 5 is a schematic diagram of a control system of the interrogationand detection system, according to one illustrated implementation.

FIG. 6 is a schematic diagram of a software configuration of theinterrogation and detection system, according to one illustratedimplementation.

FIG. 7 is a flow diagram of a method of operating an interrogation andcontrol system, according to one illustrated implementation.

FIG. 8 is a flow diagram showing a method of operating an interrogationand detection system according to one illustrated implementation,including receiving electromagnetic signals, for example unmodulatedelectromagnetic signals, determining a noise value, adjusting signaldetection threshold, emitting interrogations signals, receivingelectromagnetic signals, and determining a presence or absence of atransponder based at least in part on the adjusted signal detectionthreshold.

FIG. 9 is a graph showing noise and signal levels when the signal issampled using subsample scan cycles, according to one illustratedimplementation.

FIG. 10 is a timing diagram illustrating interrogation cycle timing,according to one illustrated implementation.

FIG. 11A is a timing diagram illustrating a scan cycle, according to oneillustrated implementation.

FIG. 11B is a timing diagram illustrating a coil scan cycle, accordingto one illustrated implementation.

FIG. 11C is a timing diagram illustrating a frequency specific samplecycle, according to one illustrated implementation.

FIG. 11D is a timing diagram illustrating a subsample scan cycle,according to one illustrated implementation.

FIG. 12 is a timing diagram illustrating timing for obtaining subsamplesutilizing subsample scan cycles, according to one illustratedimplementation.

FIG. 13 is a flow diagram showing a process for a scanning method,according to one illustrated implementation.

FIG. 14 is a flow diagram showing a process for a scanning method usedwith multiple coils, according to one illustrated implementation.

FIG. 15 is a flow diagram showing a process for implementing a dynamicinstrument scan cycle and a static instrument scan cycle, according toone illustrated implementation.

FIG. 16 is a flow diagram showing a method of determining the presenceor absence of a transponder by evaluating one or more subsamples,according to one illustrated implementation.

FIG. 17 is a bottom isometric, partially exploded view of the probe ofthe interrogation and detection system also shown in FIG. 3A.

FIG. 18 is a top isometric, partially exploded view of the probe of theinterrogation and detection system also shown in FIG. 3A.

FIG. 19A is an isometric view of the coil form of the probe of theinterrogation and detection system.

FIG. 19B is an elevational view of the coil form shown in FIG. 19A.

FIG. 20 is an isometric view of an inner surface of a right housing ofthe probe of the interrogation and detection system, illustrating analignment rib.

FIG. 21 is a sectional view of a coil of the probe, and a sectional viewof a transponder disposed proximate to the coil.

FIG. 22A is an elevational view of the coil form illustrating a radiusof a length of an outer surface of a coil form channel.

FIG. 22B is an elevational view of the coil form illustrating a radiusof a width of an outer surface of a coil form channel.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedimplementations. However, one skilled in the relevant art will recognizethat implementations may be practiced without one or more of thesespecific details, or with other methods, components, materials, etc. Inother instances, well-known structures associated with transmitters,receivers, or transceivers have not been shown or described in detail toavoid unnecessarily obscuring descriptions of the implementations.

Unless the context requires otherwise, throughout the specification andclaims that follow, the word “comprising” is synonymous with“including,” and is inclusive or open-ended (i.e., does not excludeadditional, unrecited elements or method acts).

Reference throughout this specification to “one implementation” or “animplementation” means that a particular feature, structure orcharacteristic described in connection with the implementation isincluded in at least one implementation. Thus, the appearances of thephrases “in one implementation” or “in an implementation” in variousplaces throughout this specification are not necessarily all referringto the same implementation. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more implementations.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its sense including “and/or” unless the contentclearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theimplementations.

FIGS. 1A and 1B show an environment 100 in which a medical provider 102operates an interrogation and detection system 104 to ascertain thepresence or absence of objects 106 in, or on, a patient 108. Theinterrogation and detection system 104 may include a controller 110, andone or more coil assemblies 314 (see FIG. 3D) coupled to the controller110 by one or more communication paths, for example coaxial cable 114.The antennas may be housed within a hand-held probe 112 that may includeone or more antenna coils, for example. While designated as a probe, theblunt instrument is not necessarily intended to explore a wound or toeven enter a patient's body. In many applications the hand-held probewill remain on the exterior outside of the patient's body (e.g.,proximate a joint such as a knee, ankle, shoulder, hip, or neck). Insome applications, for example labor and delivery (L&D), the patient maynot have a wound.

The object 106 may take a variety of forms, for example instruments,accessories and/or disposable objects useful in performing surgicalprocedures. For instance, the object 106 may take the form of scalpels,scissors, forceps, hemostats, and/or clamps. Also for example, theobjects 106 may take the form of surgical sponges, gauze and/or padding.The object 106 is tagged, carrying, attached or otherwise coupled to atransponder 116. Implementations of the interrogation and detectionsystem 104 disclosed herein are particularly suited to operate withtransponders 116 which are not accurately tuned to a chosen or selectedresonant frequency. Consequently, the transponders 116 do not requirehigh manufacturing tolerances or expensive materials, and thus may beinexpensive to manufacture.

In use, the medical provider 102 may position the probe 112 proximatethe patient 108 in a fixed or static position to detect the presence orabsence of the transponder 116 and hence an object 106. The medicalprovider 102 may in some implementations dynamically move the probe 112along and/or across the body of the patient 108 or may move the probenear other areas, such as a near a trash can or drape bag in a surgeryroom. As show in FIG. 1A, the probe 112 may be sized to fit at leastpartially around a knee 118 of the patient 108 to detect the presence orabsence of the transponder 116 and hence the object 106. As shown inFIG. 1B, the probe 112 may be sized to fit at least partially around ashoulder 119 of the patient to detect the presence or absence of thetransponder 116 and hence the object 106. In practice, the probe 112 maybe sized and shaped to fit at least partially around various joints ofthe patient 108.

FIG. 2A shows a transponder 116 a according to one illustratedimplementation. The transponder 116 a includes a miniature ferrite rod230 with a conductive coil 232 wrapped about an exterior surface thereofto form an inductor (L), and a capacitor (C) 234 coupled to theconductive coil 232 to form a series LC circuit. The conductive coil 232may, for example, take the form of a spiral wound conductive wire withan electrically insulative sheath or sleeve. The transponder 116 a mayinclude an encapsulant 236 that encapsulates the ferrite rod 230,conductive coil 232, and capacitor 234. The encapsulant 236 may be abio-inert plastic that protects the ferrite rod 230, conductive coil 232and/or capacitor 234 from pressure and/or from fluids, for examplebodily fluids.

In some implementations, the ferrite rod 230 may include a passage 238sized to receive a physical coupler, for example a bonding tie or string240. The bonding tie or string 240 may take the form of an elastomericx-ray opaque flexible elongated member, that may be used to attach thetransponder 116 a to various types of objects 106, for example surgicalsponges. The transponder 116 a may have a length of about 8 millimetersand a diameter of about 2 millimeters. Employing such small dimensionsensures that the transponder 116 a does not impede deformation ofobjects 106 such as sponges. The transponder 116 a may include anoptional diode (not shown), to protect against over-voltage occurrencescaused by other electronic instruments.

FIG. 2B shows a transponder 116 b, according to another illustratedimplementation. The transponder 116 b includes a single loop ofconductive material 242, for example a loop of conductive wire formingan inductor (L), coupled in series to a capacitor 244 (C) to form an LCseries circuit. The loop of conductive material 242 and capacitor 244may be encapsulated in an elastomeric coating or sleeve 246. Thedimensions of the transponder 116 b may be similar to the dimensions ofthe transponder 116 a. In some implementations, the dimensions of thetransponder 116 b are greater than the dimensions of the transponder 116a. The transponder 116 b is highly flexible, and thus may provide itsown thread-like or string-like attachment to various types of objects106.

FIG. 2C shows a transponder 116 c according to a further implementation.The transponder 116 c includes a dumbbell-shaped ferrite rod 248 havingbroad end portions 248 a, 248 b, and a narrow intermediate portion 248 cwhich is wrapped by a conductive coil 250. The broad end portions 248 a,248 b contain the conductive coils 250. Such a design may providestronger and/or more reliable signal emission than transponders 116 a,116 b fashioned with cylindrical ferrite rods. The transponder 116 c mayoptionally include an encapsulant 252. Further details regarding thetransponder 116 c may be found in U.S. Provisional Patent ApplicationNo. 60/811,376 filed Jun. 6, 2006, incorporated herein by reference. Insome implementations, the transponder 116 c may be formed as afusiform-shaped object, with truncated ends. The fusiform shape may beadvantageous over cylindrical shaped transponders 116 a, 116 b inreducing the likelihood of close parallel alignment of the transponders116 a, 116 b, which may produce transponder-to-transponder interactionand interference.

FIGS. 2D-2G show a transponder 116 d according to yet a furtherimplementation. The transponder 116 d includes a ferrite core 253,inductor (L) 254, and capacitor (C) 255 electrically coupled to theinductor 254 to form an LC series circuit. The transponder 116 d alsoincludes a capsule 256 with a cavity 257 open at one end to receive theferrite core 253, inductor 254 and capacitor 255, as well as a lid 258to close the open end of the capsule 256.

The ferrite core 253 may, for example, take the form of a soft ferritedrum, and may, for example, be formed of Nickel Zinc. Suitable ferritecores 253 may be commercially available from TAK FERRITE as part no. L8ADR3X9 B=1.8 F=6 or from HUAH YOW under part no. 10R030090-77S. The drummay have a pair of larger diameter end portions 253 a, 253 b, with asmaller diameter intermediate portion 253 c therebetween.

The inductor 254 may take the form of magnet wire wrapped around theintermediate portion 253 c of the ferrite core 253. The magnet wire may,for example, have a dimension of approximately 41 American Wire Gauge(AWG), although some implementations may employ wires or conductors oflarger or small gauges. Suitable inductors 254 may be commerciallyavailable from ELEKTISOLA under part no. PN-155 or from ROSEN under partno. 2UEW-F. The inductor may, for example, include approximately 432turns, over approximately 6.5 layers, although some implementations mayinclude a greater or lesser number of turns and/or layers. Thetransponder 116 d may include tape and/or epoxy enveloping the inductor254. Suitable tape may be commercially available from 3M under part nos.1298, 1350-1 or PLEO 1P801, while suitable epoxy may be commerciallyavailable from LOCKTITE under part no. 3211.

The capacitor 255 may, for example, take the form of a ceramiccapacitor. The capacitor 255 may, for example, have a capacitance of470PF, 100V, with a Quality factor of Q>2200 @ 1 MHz. Suitablecapacitors 255 may be commercially available from SANJV DIELECTRIC underpart no. 0805NPO471J101 or from FENG HUA under part no. 0805CG471J101NT.

The capsule 256 and lid 258 may, for example, be formed of apolypropylene. Suitable capsules 256 and lids 258 may be commerciallyavailable from WEITHE ELECTRON (HK) COMPANY, under part specificationCASE 4.3×12.6. The combination of the capsule 256 and lid 258 may, forexample, have a length of approximately 12.8 mm and a diameter of 4.4mm. Circuit bonds may, for example, employ UNITED RESINS CORP. part no.63001500 CIRCUIT BOND LV, while solder may take the form of a lead free96.5% Ag/3% Sn/0.5 Cu solder.

The transponders 116 may be attached to hemostats, scissors, certainforms of forceps, and the like. In some implementations, thetransponders 116 may be coupled to the object 106 by way of a clamp orholder. In some implementations, the transponders 116 may be retainedwithin a cavity of the holder. In some implementations, the holder maybe fashioned of a durable deformable material, such as surgical gradepolymer, which may be deformed to clamp securely onto the finger orthumbhole of an instrument. In other implementations, the transponders116 may be attached to objects 106 by way of pouches fashioned of sheetmaterial (e.g., surgical fabric) surrounding the transponder 116. Thetransponder 116 is retained within the pouch, and in someimplementations the pouch may be sewn or otherwise sealed. Sealing maybe done with adhesive, hot glue, clamping, grommeting, or the like.

FIGS. 3A-3D, 17, 18, 19A-19B, 20, 21, 22A and 22B show various views ofthe probe 112 also shown in FIGS. 1A-1B, according to one illustratedimplementation.

As shown in FIGS. 3A, 3B, 17 and 18, the probe 112 includes a bottomhousing 302 having a distal or front end portion 304 and a proximal orrear end portion 306 spaced apart from the front end portion. The probe112 also includes a front top housing 308 that mates to the front endportion 304 of the bottom housing 302 to form a substantially sphericalfront body portion 310 that defines a cavity 312 that accommodates afront coil assembly 314 therein. The probe 112 also includes a rear tophousing 316 that mates to the rear end portion 306 of the bottom housing302 to form a substantially spherical rear body portion 318 that definesa cavity 320 that accommodates a rear coil assembly 322 therein.

The probe 112 may also include a top middle housing 324 that mates witha middle portion 326 of the bottom housing 302 between the front endportion 304 and the rear end portion 306 of the bottom housing to form acavity 328 that accommodates a circuit board 330 electrically coupled tothe front coil assembly 314 and the rear coil assembly 322. The circuitboard 330 may be coupled to the middle portion 326 of the bottom housing302 via one or more fasteners (e.g., screws 332). The front and rear tophousings 308, 316 and the top middle housing 324 may be fixedly coupledto the bottom housing 302 during manufacture by any suitable process(e.g., an adhesive such as LOCTITE 414®, RF welding, friction fit, snapfit, tabs and lips, pins and holes, detents, etc.). The middle portions324, 326 of the probe 112 may form a handle portion 334 extendingbetween the spherical body portions 310 and 318. The handle portion 334may be sized and dimensioned to be gripped by the hand of the medicalprovider 102 (FIGS. 1A-1B). In some implementations, the handle portion334 may include an overmolded gripping surface. The overmolded grippingsurface may be a material that provides a relatively high degree of tactand/or may be textured to facilitate non-slip gripping. In someimplementations, the handle portion 334 may be shaped similar to that ofa conventional phone, which is ergonomically desirable for the medicalprovider 102. Further, as shown best in FIG. 3C, the handle portion 334is curved or bent between the first body portion 310 and the second bodyportion 318 to allow the first body portion and the second body portionto at least partially surround a joint 121 during use. The handleportion 334 and the body portions 310 and 318 together form an invertedtrough or “U-shape” that forms a joint receiving portion 335 whichreceives the joint 121 during use. Thus, the body portions 310 and 318may both be positioned simultaneously against sides of the joint 121 toincrease the likelihood that a transponder 116 will be detected.

As noted above, the front and rear body portions 310 and 318 may definerespective front and rear cavities 312 and 320 (FIG. 17) sized anddimensioned to receive the front and rear coil assemblies 314 and 322,respectively. FIGS. 3D, 19A-19B and 22A-22B show various views ofportions of the front coil assembly 314. The rear coil assembly 322 maybe substantially identical to the front coil assembly 314, so thediscussion below regarding the front coil assembly also applies to therear coil assembly.

The front coil assembly 314 may, for example, take the form of anair-coil formed of coils of conductive material, for example, electricalwire. The front coil assembly 314 acts as an inductor that facilitatesmagnetic inductive coupling with one or more coils of a transponder 116.

As shown in FIG. 3D, the front coil assembly 314 may include threeantenna coils: a radially inner coil 338 a, a radially middle coil 338b, and a radially outer coil 338 c mutually orthogonal to each other. Inthe illustrated implementation, the antenna coils 338 a, 338 b, and 338c are wound around outer surfaces 340 a, 340 b, 340 c, respectively(FIG. 19A), of respective coil form channels 342 a, 342 b, and 342 c ofa coil form or bobbin 344. Electrical wires or ends 346 a, 346 b, and346 c (FIG. 3D) of the respective coils 338 a, 338 b, and 338 c may beelectrically coupled to the PCT 330, which may be coupled to thecontroller 110 via the cable 114 (FIGS. 1A-1B). In some implementations,the coil form 344 may be a flexible printed circuit board (e.g.,relatively few laminations of FR4). The coil form 344 may include strainrelief structures or features such as notches, or cutouts laterallyacross the width of the printed circuit board and/or extending into thesurface or along the edges of the printed circuit board.

As shown in FIGS. 17 and 18, the electrical wires 346 a, 346 b, and 346c, of the respective coils 338 a, 338 b, and 338 c may be coupled to theprinted circuit board 330, which may in turn be coupled to wires 348 ofa coupling member 350, which may be positioned in the cavity 320 in therear body portion 318 to provide a connector to communicatively coupleto an end of the coaxial cable 114 to the antenna coils of the first andsecond coil assemblies 314 and 322. The coupling member 350 may take theform of a standard coaxial connector, for example. Some implementationsmay employ other types of wired and/or wireless communications pathwaysbetween the controller 110 and the coil assemblies 314 and 322, and thusmay employ other types of coupling members or connectors.

In some implementations, the probe 112 may include one or more userinterface devices, for example one or more visual indicators 352 (FIG.3A) to provide visual indications to the medical provider 102. Such may,for example, take the form of one or more light emitting diodes 354(FIG. 17), which may provide one or more different colors. Such userinterface devices may additionally or alternatively include a speaker orother transducer (e.g., piezoelectric transducer, electric motor),operable to provide a sound or other sensory indication, for example atactile sensation (e.g., vibration). Such user interface devices may beoperable to provide sensory feedback to the medical provider 102indicative of an operating condition of the interrogation and detectionsystem 104. For example, such may indicate when the interrogation anddetection system 104 is operating, when the presence of a transponder116 has been identified, and/or when an error has occurred. Locatinguser interface devices on the probe 112 may be advantageous since themedical provider 102 will typically focus their attention on the probe112 while scanning the patient 108.

In the illustrated implementation, the printed circuit board 330includes the light emitting diode 354 (FIG. 17) coupled thereto. A lightpipe 356 may be positioned within an aperture 358 of the front tophousing 308. The light pipe 356 is light transmissive such that lightfrom the light emitting diode 354 may pass through the light pipe whereit is visible by a user. The light emitting diode 354 may be used toprovide a visual indication to a user of the probe 112, such as statusinformation or operational information.

As shown in FIGS. 3D, 19A and 19B, the generally spherical coil form 344includes the three mutually orthogonal coil form channels 342 a, 342 b,and 342 c each having a respective outer surface 340 a, 340 b, and 340 cfor supporting a respective one of the coils 338 a, 338 b, and 338 c. Asshown in FIG. 19A, the first coil form channel 342 a is oriented in anXY plane, the second coil form channel 342 b is oriented in an XZ plane,and the third coil form channel 342 c is oriented in a YZ plane. Thethree coil form channels 342 a, 342 b, and 342 c may intersect eachother or may be nested. Each of the three coil form channels 342 a, 342b, and 342 c defines its respective outer coil support surface 340 a,340 b, and 340 c. Each outer coil support surface 340 a, 340 b, 340 c issubstantially cylindrically shaped with a curved surface. Morespecifically, in the illustrated implementation each outer coil supportsurface 340 a, 340 b, and 340 c is shaped as a spherical zone of avirtual sphere, the spherical zone having a width W (FIG. 19B) and beingcentered on a great circle of the virtual sphere. As used herein, agreat circle of a sphere is the intersection of the sphere and a planewhich passes through the center point of the sphere. As used herein, aspherical zone is the surface of a spherical segment, which is a soliddefined by cutting a sphere with a pair of parallel planes. In thiscase, the parallel planes are also parallel to a great circle of thevirtual sphere and spaced apart on each side of the great circle by anequal distance (i.e., W/2), such that the spherical segment is centeredon the great circle.

As shown in FIGS. 22A and 22B, each of the outer coil support surfaceshave a circumference or length L that is defined by a body of revolutionabout a respective primary axis and a width W that is curved about arespective secondary axis orthogonal to the primary axes. Specifically,the length L of the outer coil support surface 340 a is defined by arevolution about the Z axis (FIG. 22A) and the width W is curved aboutthe X axis (FIG. 22B). The length L of the outer coil support surface340 b is defined by a revolution about the Y axis and the width W iscurved about the Z axis. The length L of the outer coil support surface340 c is defined by a revolution about the X axis and the width W iscurved about the Z axis.

The curvatures of the length L and the width W of each of the outer coilsupport surfaces 340 a-340 c are equal to each other. For example, thelength L of the outer coil surface 340 a at its center may be defined bya circle in the XY plane having a curvature radius R_(L-340a) (FIG.22A). The width W of the outer coil surface 340 a has a radius ofcurvature of R_(W-340a) (FIG. 22B), which is equal to the radiusR_(L-340a) of the length L.

As shown in FIGS. 19A and 19B, eight apertures 360 shaped as sphericaltriangles may be defined by the intersection of the coil form channels342 a, 342 b, and 342 c. The size of the eight apertures 360 isdependent on the width W of the coil form channels 342 a, 342 b, and 342c. That is, the wider the width W of coil form channels 342 a, 342 b,and 342 c, the smaller the eight apertures 360. In some implementations,the apertures 360 are not present and the coil form 344, such that thecoil form is substantially shaped as a sphere without apertures therein.In some implementations, the interior of the coil form 344 may behollow, whereas in other implementations one or more materials may bepresent within the interior of the coil form.

As shown in FIG. 20, an interior surface 362 of the front top housing308 may include an alignment rib 364 shaped and sized to be insertedinto one of the spherical triangle-shaped apertures 360 of the coil form344. The front end portion 304 of the bottom housing 302 may alsoinclude an alignment rib 366 on an interior surface 368 thereof. Thealignment ribs 364 and 366 on the respective interior surfaces 362 and368 of the housings 308 and 302 align the coil form 344 relative to thehousings during manufacturing and fix the position of the coil form withrespect to the assembled housing. The coil form 344 may be secured tothe front end portion 304 of the bottom housing 302 and the front tophousing 308 by a suitable adhesive (e.g., PC-11 A and PC-11 B two-partepoxy). The rear coil assembly 322 may be secured to the rear endportion 306 of the bottom housing 302 and the rear top housing 316 in asimilar manner.

As shown in FIG. 3D, the first coil 338 a is wound around the outer coilsupport surface 340 a of the first coil support channel 342 a to form afirst antenna element arranged in the XY plane so as to transmit andreceive signals primarily in the orthogonal z-axis direction. The secondcoil 338 b is wound around the outer coil support surface 340 b of thesecond coil support channel 342 b over the first coil 338 a to form asecond antenna element in the XZ plane so as to transmit and receivesignals primarily in the orthogonal y-axis direction. The third coil 338c is wound around the outer coil support surface 340 c of the third coilsupport channel 342 c over the first coil 338 a and over the second coil338 b to form a third antenna element in the YZ plane so as to transmitand receive signals primarily in the orthogonal x-axis direction.

By providing three mutually orthogonal coils within the front bodyportion 310 of the probe 112 and three mutually orthogonal coils withinthe rear body portion 318, the likelihood of detecting a transponder ata given distance is improved. This is illustrated with reference to FIG.21, which shows a sectional view of the second coil 338 b disposed inthe XZ plane and configured to transmit and receive signals primarily inthe orthogonal y-axis direction, and a sectional view of the transponder116 d positioned proximate to the second coil. The efficiency of thecoupling between the second coil 338 b and the inductor or coil 254 ofthe transponder 116 d is proportional to the presentation angle of thetwo coils relative to each other. Maximum coupling occurs when the twocoils are in a parallel relationship (i.e., an angle Θ=0 degrees). Thiscondition results in maximum induced voltage in the transponder coil 254and a maximum read range. As the transponder 116 d is rotated withrespect to the second coil 338 b, the magnetic coupling is reduced bythe cosine of the angle of rotation (i.e., a cosine Θ variation). Thus,when the two coils 338 b and 254 are in a perpendicular relationship(i.e., angle Θ=90 degrees), magnetic coupling is minimized (e.g., a“dead zone”). Under conditions of minimum coupling, it is less likelythat the second coil 338 b will be able to detect the transponder 116 d.

By utilizing two sets of three mutually orthogonal coils 338 a-338 c, asopposed to a single planar coil, the ability to detect a transponder issignificantly improved. For example, for each set of mutually orthogonalcoils, it is possible to ensure that the angle Θ of rotation of thetransponder coil 254 will always be less than 45 degrees with respect toat least one of the orthogonal coils 338 a-338 c. At an angle Θ ofrotation of 45 degrees (i.e., “worst case” orientation), the magneticcoupling is approximately 71% of the maximum or optimum magneticcoupling (i.e., cosine 45 degrees=0.707). Thus, the use of threeorthogonal coils 338 a-338 c ensures that the magnetic coupling betweenthe transponder coil 254 and at least one of the coils 338 a-338 c ofthe probe 112 will always be at least 71% of the maximum couplingorientation. Accordingly, given the same transmit energy, transponders116 may be detected at a greater distance using the two sets of threeorthogonal coils 338 a-338 c as compared to using a single planar coil.Additionally or alternatively, the probe 112 may transmit signals atlower energy levels to achieve a similar read range as a single planarcoil transmitting at a higher energy level.

In the illustrated implementation, the respective second supportchannels 342 b of the first coil assembly 314 and the second coilassembly 316 are oriented to be coplanar in an XZ plane to transmit andreceive signals primarily in the orthogonal y-axis direction. Therespective first support channels 342 a of the first coil assembly 314and the second coil assembly 316 are oriented to be parallel andnon-coplanar in an XY plane to transmit and receive signals primarily inthe orthogonal z-axis direction. The respective third support channels342 c of the first coil assembly 314 and the second coil assembly 316are oriented to be parallel and non-coplanar in a YZ plane to transmitand receive signals primarily in the orthogonal x-axis direction. Inother implementation, the respective support channels of the first coilassembly 314 and the second coil assembly 322 may aligned differentlywith respect to each other.

FIG. 4 shows the controller 110 according to one illustratedimplementation. The controller 110 includes an input port 420 with anappropriate coupling member, for example a connector to allow an end ofthe coaxial cable 114 to be communicatively coupled to the controller110. As noted above, some implementations may employ othercommunications pathways between the controller 110 and the coilassemblies 314 and 322, hence other types of coupling members orconnectors may be employed. The controller 110 may also include a powerswitch (not illustrated in FIG. 4), for example, positioned on a back orrear of the controller 110. The controller 110 may further include apower cord (not shown) to couple the controller 110 to a suitable powersupply. The power supply may, for example take the form of a standardwall outlet or any other power supply or source. The controller 110 mayfurther include one or more user interface devices for providinginformation to a user. For example, the controller 110 may include oneor more visual indicators, for instance one or more light emittingdiodes (LEDs) 434 a-434 f and/or liquid crystal displays. Additionally,or alternatively, the controller 110 may include one or more speakers430 or other transducers operable to produce sound or tactilesensations. The controller 110 forms a transmitter and receiver, ortransceiver, to transmit interrogation signals and receive responses tothose signals, as well as to receive electromagnetic signals which maybe indicative of noise.

FIG. 5 shows a control system 500 of the interrogation and detectionsystem 104, according to one illustrated implementation.

The control system 500 includes a field programmable gate array (FPGA)board 502, analog board 504 and display board 506, communicativelycoupled to one another. The FPGA board includes an FPGA 508,configuration jumpers 510, RS-232 drivers 512, oscillator 514, randomaccess memory (RAM) 516, flash memory 518, and voltage monitoring (VMON)analog-to-digital converter (ADC) 520. The FPGA 508 may take the form ofa Xilinx Spartan3 FPGA, which runs FPGA and application software. Asexplained below, on power up, the FPGA reads the configurationinformation and application software program from the flash memory 518.

The configuration jumpers 510 are used to select the applicationsoftware configuration.

The RS-232 drivers 512 are used to allow the application software tocommunicate using serial RS-232 data for factory test and diagnostics.

The oscillator 514 sets the clock frequency for the operation of theFPGA 508. The oscillator 514 may, for example, take the form of 40 MHzoscillator, although other frequencies are possible.

The RAM 516 is connected to the FPGA 508 and is available for use by theapplication software. The application software uses this memory spacefor storage of both the executable program and program data. The RAM 516may, for example, have a capacity of 1 MB.

The flash memory 518 contains both the FPGA configuration data and thebinary application program. On power up the FPGA 508 reads the flashmemory to configure the FPGA 508 and to copy the application programbinary data from the flash memory 518 to the RAM 516.

The voltage monitor ADC 520 is connected to the FPGA 508 and controlledby the application software to monitor a power supply and regulatedvoltage forms in controller electronics.

The analog board 504 includes transmit control circuits 522, capacitorselection circuits 524, probe detection circuit 526, signal ADC 528,audible beeper 430 and self-test signal 532.

The transmit control circuits 522 on the analog board 504 are controlledby signals from the FPGA 508 to generate a transmit waveform.

Optional capacitor selection circuits 524 on the analog board 504 arecontrolled by the signals from the FPGA 508 to tune the drive circuit tomatch an inductance of the antennas of the coil assemblies 314 and 322.

The probe detection circuit 526 detects when a probe 112 is connected tothe controller 110. The output of the probe detection circuit 526 drivesa signal denominated as the LOOP_LEVEL_OUT signal, which is an input tothe FPGA 508.

The signal ADC 528 is used as a receiver to sample the signals receivedat the coil assemblies 314 and 322 from the transponders 116 (FIGS.2A-2C). The signal ADC 528 may, for example, operate at a 1 MHz samplerate and may have 12-bits of resolution. The FPGA board 502 generatesthe timing and control signals for the signal ADC 528, which signals aredenominated as ADC_CTRL, CS1, SCLK, and SD0.

The audible speaker or beeper 430 can be controlled by the FPGA 508 toemit sounds to indicate various states, modes or operating conditions tothe medical provider 102 (FIGS. 1A-1B).

The FPGA 508 can cause the generation of the self-test signal 532 on theanalog board 504 at the signal ADC 528. Self-testing may be performed atstart up, and/or at other times, for example periodically or in responseto the occurrence of certain conditions or exceptions.

The display board 506 includes user interface elements, for example anumber of light emitting diodes (LEDs) 434. The FPGA board 502 cancontrol the LEDs 434 on the display board 506. The display board 506also includes a user selectable activation switch, denominated as frontpanel button 436. The front panel button 436 is connected to the displayboard 506 which allow the FPGA 508 to monitor when the front panelbutton 436 is activated (e.g., pressed).

FIG. 6 shows a software configuration 600 of the interrogation anddetection system 104, according to one illustrated implementation.

The software may include application software 602 that is responsiblefor operating the controller 110 (FIGS. 1A-1B and 4). The applicationsoftware 602 controls the timing for generating transmit pulses,processes sampled data to detect transponders 116 (FIGS. 2A-2C), andindicates status to the user with the display LED's 434 (FIG. 5) on thedisplay board 506 and/or via the audible speaker or beeper 130 on theanalog board 504. The application software 602 is stored in the flashmemory 518 (FIG. 5) and transferred into the RAM 516 by a boot loader604.

The boot loader 604 is automatically loaded when the FPGA 508 isconfigured, and starts execution after a processor core 606 is reset.The boot loader 604 is responsible for transferring the applicationsoftware 602 from the flash memory 518 to the external RAM 516.

The processor platform 608 is configured into the FPGA 508 (FIG. 5) onpower up from the configuration information stored in the flash memory518. The processor platform 608 implements a custom microprocessor witha processor core 606, peripherals 610 a-610 n, and custom logic 612.

The processor core 606 may take the form of a soft processor coresupplied by XILINX under the name MICROBLAZE that implements a 32-bitprocessor including memory cashes and a floating point unit. A soft-coreprocessor is one that is implemented by interconnected FPGA logic cellsinstead of by traditional processor logic. The processor core 606 isconnected to the internal FPGA peripherals 610 a-610 n using a 32-bitprocessor bus 611 called the On-Chip Peripheral Bus. The XILINX suppliedperipherals for the MICROBLAZE processor core 606 include externalmemory interfaces, timers, and general purpose I/O.

The custom logic 612 to create the transmit signals, sample the ADC 128,and accumulate the transponder return signals is designed as aperipheral to the processor core 606. The custom logic 612 is the partof the design of the FPGA 508.

In some implementations, a detection cycle that employs an approach thatoptimizes signal to noise ratio (SNR) by a receiver portion may beimplemented. Such may, for example, advantageously increase range orincrease sensitivity at a given range. One implementation is optimizedbased on having an overall detection cycle that performs well fortransponders with resonant frequencies from approximately 136 kHz toapproximately 154 kHz.

The application software 602 (FIG. 6) implements the detection cycleusing transmission or interrogation in a frequency band centered arounda center channel or frequency. The application software 602 sequencesthrough a non-measurement portion (i.e., gap), and two distinctmeasurement portions, denominated as a noise detection portion and asignal measurement portion, each detection cycle. In at least oneimplementation, the detection cycle may, for example, be approximately275 milliseconds, the gap portion may be approximately 10 milliseconds,the noise portion approximately 37 milliseconds and the signalmeasurement portion approximately 228 milliseconds.

During the noise detection portion, which may, for example be a firstmeasurement portion of each detection cycle, ambient or background noiseis measured or sampled, providing a value indicative of a level ofambient or background noise for the particular environment. The noisemeasurements or are taken or captured at a time sufficiently afterexcitement of the transponders 116 by the interrogation signal emittedby the transmitter such that the transponders 116 are substantially notresonating or responding to any previous excitation by interrogationsignals. In particular, a number N of measurements or samples are takenduring the noise detection or first measurement portion.

During the signal measurement portion which may, for example, take theform of the second measurement portion of each detection cycle,responses by transponders 116 are measured or sampled. The responsemeasurements or samples are taken with the transmitter transmitting orat a time sufficiently close to excitement of the transponders 116 bythe interrogation signal emitted by the transmitter such that thetransponders 116 are still substantially resonating or responding to theinterrogation signal. In particular, a number M of measurements orsamples are taken during the interrogation or second measurementportion.

While the signal measurement portion may be one contiguous or continuousportion, in some implementations the signal measurement portion may takethe form of two or more separate portions or intervals. Each of theportions may employ the same transmit frequency band, for examplecentered around 145 kHz. Other center channels or frequencies may forexample be 136 kHz, 139 kHz, 142 kHz, 145 kHz, 148 kHz, 151 kHz and/or154 kHz, or any other frequency suitable for exciting the transponder toresonate. Some implementations may employ frequency hopping, for exampletransmitting a different center channel or frequency for each of aplurality of signal measurement portions of each detection cycle. Suchis discussed further in U.S. provisional patent application Ser. No.60/892,208, filed Feb. 28, 2007 and U.S. non-provisional applicationSer. No. 11/743,104, filed May 1, 2007.

The gap portion may provide time for the response of the transponders116 to the interrogation signal to decay sufficiently to allowmeasurement of noise.

Some implementations may arrange the gap, the noise detection portionand/or the signal measurement portion, or parts thereof, in a differentorder.

In one implementation, the time to accumulate the noise sample or valueindicative of a noise level may, for example, be approximately 37milliseconds, and the time to accumulate the transponder signalmeasurement approximately 228 milliseconds. Along with a gap ofapproximately 10 milliseconds between the signal and noise portions, thetime for a single detection cycle would be approximately 275milliseconds. As noted above, the transmitter is OFF during the noisemeasurement portion of each detection cycle to allow the receiver tomeasure ambient noise, and the signal detection portion is taken withthe transmitter transmitting a wideband interrogation signal about theparticular center channel or frequency.

The noise samples collected by the receiver may be accumulated and ahighest one or more of multiple samples or measurements over one or moredetection cycles selected or used to prevent unwarranted fluctuations.The response signals from the transponder 116 may be accumulated and/oraveraged or integrated over one detection cycle or over multipledetection cycles.

The number N of noise measurements or samples and/or the number M ofresponse signal measurements or samples may be selected to achieve adesired ratio of N to M, in order to achieve or maintain a desiredsignal to noise ratio. For example, obtaining 200 noise measurements orsamples and 800 response measurements or samples each detection cycleresults in an SNR of approximately 2 (e.g., the square root of 800divided by 200). While an SNR as low as 1.1:1 may be sufficient in someimplementations, an SNR approaching 2:1 ensures sufficientdifferentiation to eliminate or reduce the possibility of falsepositives to an acceptable level for the particular applicationsenvisioned herein. Any known hardware and software accumulators,summers, integrators and/or other hardware or software may be suitable.

The accumulated or integrated received signal may be matched filteredwith both in-phase and quadrature reference signals to determine thesignal magnitude. The received receive signal is matched filtered with aplurality of reference signals, for example with the seven referencesignals, for instance as shown in Table 1 below. Some implementationsmay employ matched filtering before accumulating or integrating thereceived signal.

TABLE 1 Match Frequency 136 kHz 139 kHz 142 kHz 145 kHz 148 kHz 151 kHz154 kHz

The maximum value for the matched filters (e.g., seven matched filters)with active transmit may be compared with an adjusted detectionthreshold. If the maximum value is greater than the detection threshold,then a response signal from a transponder 116 may be considered ashaving been detected, and appropriate action is taken, such as discussedbelow with reference to FIG. 7. Alternatively or additionally, theinterrogation and detection system may employ a fast Fourier transformapproach in lieu of matched filtering.

The noise filtering processes the measured or sampled noise values foreach detection cycle to determine a stable noise floor value. The outputof the noise filter may, for example, be the maximum of either thecurrent noise measurement or a decayed value of the previous noisefloor.

The output of the noise filter may be an estimate of the current noisefloor level after selecting the highest of a plurality (e.g., 6) ofnoise measurements or samples. The filtered noise floor mayadvantageously include samples collected, captured or measured bothbefore and after a given signal sample is collected, captured ormeasured. Thus, for any sample of a given detection cycle the noisefloor may include noise samples from the given detection cycle, as wellas a next successive detection cycle. The filtered noise floor mayadditionally, or alternatively, include noise samples from one or moresuccessively preceding detection cycles, as well as one or moresuccessfully succeeding detection cycles.

FIG. 7 shows a method 700 of operating the interrogation and detectionsystem 104 according to one illustrated implementation.

In response to detecting a disconnect of power, the interrogation anddetection system 104 enters a Power OFF mode at 702. For example, thePower OFF mode 702 may be entered when the controller 110 (FIGS. 1A-1Band 4) is unplugged or when the power switch on the controller 110 isturned OFF. In the Power OFF mode 702, the Power LED 434 a and otherfront panel LEDs 434 will be turned OFF (non-emitting). The software 700is inoperative in the Power OFF mode 702.

In response to detecting an application of power, the interrogation anddetection system 104 enters a Power-Up mode 704. The Power UP mode 704may, for example, in response to the application of power to thecontroller 110 and turning ON the switch on the back of the controller.In the Power-Up mode 704, a Power LED 434 a may be turned ON orilluminated, and may remain ON or illuminated as long as the power isapplied and the switch is in the ON state. In response to entering thePower UP mode 704, the software 700 will perform softwareinitialization, built in tests, and an audio/visual test.

If a fault is detected, the software 700 progresses to a System FaultMode 706. If no faults are detected, the software 700 may turn a SystemReady LED green, and enter a Probe Detection Mode 708.

In the System Fault Mode 706, the software 700 may cause an indicationof the detection of a system fault by blinking a System Ready LED 434 byellow, and/or issuing a sequence of rapid beeps or other sounds. Thecorrective action for the System Fault Mode 706 is to cycle power toreinitiate the Power Up mode 704. Continued failure indicates a failedcontroller 110.

In the Probe Detection Mode 708, the software 700 checks for a probe 112connected to the controller 110. The Probe Detection Mode 708 may beindicated by turning the System Ready LED 434 b green and turning theProbe Ready LED 434 c OFF. If no probe 112 is detected, the software 700remains in the Probe Detection Mode. If a probe 112 is detected, thesoftware 700 progresses to the Probe Initialization Mode 710.

At the start of the Probe Initialization Mode 710, after the detectionof a probe 112, the software 700 may turn the Probe Ready LED 434 cyellow and check for the presence of a fuse in the probe 112. If a fuseis found, the software 700 may attempt to blow the fuse and verify thatthe fuse was correctly blown. After the fuse is blown the software 700may verify that probe 112 is operating within tolerances. The software700 may indicate that the probe 112 is ready by turning the Probe ReadyLED 434 c green. The software 700 may also start a timer which willallow the probe 112 to be disconnected and reconnected to the controllerfor a period to time (e.g., 5 hours) after the fuse is blown.

The controller 110 may determine the adjustments or fine tuning to bemade about the center frequencies or channels during ProbeInitialization Mode 710. In particular, the controller 110 may determinethe particular frequency in each of the frequency bands that elicits theresponse with the highest voltage. The controller may determine such byvarying the capacitance of the LC circuit using the switched capacitorsC33-C36 during the Probe Initialization Mode 710. The particularcombination of switched capacitors C33-C36 which achieved the responsewith the highest voltage may then be automatically employed during aScan Mode 714 (discussed below) to adjust or fine tune about the centerfrequency or channel in each broad band of transmission. Otherapproaches to determining the fine tuning may be employed.

If the software 700 does not successfully complete the ProbeInitialization Mode 710, the software 700 enters an Invalid Probe Mode712. If the software 700 successfully completes the Probe InitializationMode 710, the software 700 progresses to the Scan Mode 714 toautomatically start scanning.

In the Invalid Probe Mode 712, the software 700 may blink the ProbeReady LED 434 c yellow and issues a slow beep pattern.

The Invalid Probe Mode may be entered in response to any of thefollowing conditions:

The probe 112 connected to the controller 110 is out of tolerance.

The controller 110 is unable to blow the fuse in the probe 112.

The probe 112 does not have a fuse and more than the set time period haspast (e.g., 5 hours) since a fuse was blown.

The probe 112 does not have a fuse and the controller 110 has beenrestarted.

The probe 112 has been connected to the controller for more than the settime period (e.g., 5 hours).

The probe 112 is detuned due to close proximity to metal.

The corrective action for the Invalid Probe Mode 712 is to remove theinvalid probe 112 and attach a new probe 112 to the controller 110 thatcontains a fuse or to reconnect the probe 112 while holding it in theair at least 2 feet away from large metallic objects.

The software 700 enters the Scan Mode 714 when the probe 112 is readyand the operator presses a Start/Stop button. The software 700 may issuea short three beep pattern via the speaker or beeper 130 when enteringthe Scan Mode 714 to identify the entry to the user.

In the Scan Mode 714, the software 700 may continuously or periodicallyperform the following functions.

Look for response signals from transponders 116

Monitor the noise level

Insure the probe 112 is connected and operating correctly

Blink the LED's in a circular pattern

When the operator or user pushes the Start/Stop button or the a scanmaximum time interval (e.g., 4 minute) has been reached, the software700 may issue a short three beep pattern and return to the Probe ReadyMode 716.

When an appropriate response signal from a transponder 116 is detectedwhile in Scan Mode 714, the software 700 may turn ON an amber DETECTLEDs 434 d and/or provide an audible alarm. The alarm may, for example,beep a continuous solid tone as long as the transponder is detected,with a minimum of beep duration of, for instance 0.5 second.

If the software 700 detects the probe 112 is disconnected while in theScan Mode 714, the software 700 enters the Scan Fault Mode 720. In theScan Fault Mode 720, the software 700 may issue a sequence of rapidbeeps and blink ON and OFF the amber DETECT LEDs 434 d. The Scan FaultMode 720 can be cleared by pushing the Start/Stop button. The software700 will automatically clear the Scan Fault Mode 720 after 10 beeps.

While in the Scan Mode 714, if excess noise or loss of transmit signalis detected, the software 700 will progress to the Environment ErrorMode 722. In the Environment Error Mode 722, the software 700 may issueor produce an appropriate indication. For example, the software 700 maycause the production of a sequence of slow beeps and the blinking ON andOFF the green circle LEDs 434 e. The corrective action for theEnvironment Error Mode 722 is to reposition the probe 112 away fromlarge metal objects or sources of electrical interference. The software700 will automatically stop the scan if the environment error conditionlasts for more than a set time or number of beeps (e.g., 5 beeps).

FIG. 8 shows a method 800 of operating an interrogation and detectionsystem, according to one illustrated implementation. The method 800 maybe implemented by any of the interrogation and detection systemimplementations discussed above.

During each of a plurality of detection cycles, the interrogation anddetection system performs a number of acts 802-812. At 802, theinterrogation and detection system receives electromagnetic signals, forexample unmodulated electromagnetic signals, during a noise detectionportion of the detection cycle. The below descriptions will be presentedin terms of unmodulated electromagnetic signals due to the uniquetechnical advantages realized by a system that employs simple resonanttransponders without any on-board memory or storage, and from whichinformation cannot be read from or written to. However, someimplementations may employ readable and/or writable transponders, forinstance radio frequency identification (RFID) transponders or tags,which respond with a modulated electromagnetic signal that encodesinformation in the modulation. The various techniques described hereinare applicable to such transponders and modulated electromagneticsignals.

At 804, the interrogation and detection system determines a noise valueindicative of a noise level that corresponds to a highest one of anumber N of samples or measurements of the unmodulated electromagneticsignals received during the noise detection portion of the detectioncycle, where the number N is greater than one. At 806, the interrogationand detection system adjusts a signal detection threshold based at leastin part on the determined noise value of at least one of the detectioncycles.

At 808, the interrogation and detection system emits at least oneelectromagnetic interrogation signal during a transmit portion of thedetection cycle. At 810, the interrogation and detection system receivesunmodulated electromagnetic signals during a receive response portion ofthe detection cycle that follows the transmit portion of the detectioncycle.

At 812, the interrogation and detection system determines the presenceor absence of a transponder based at least in part on a number M ofsamples or measurements of the unmodulated electromagnetic signalsreceived during the detection cycle and the adjusted signal detectionthreshold, where the number M is greater than one. A ratio of N:M may beat least equal to 4. N may be equal to about 200 and M may be equal toabout 800, for example.

The interrogation and detection system may determine a noise valueindicative of a noise level based at least in part on the unmodulatedelectromagnetic signals received during the noise detection portion ofthe detection cycle by setting the noise value based on the highest oneof six samples or measurements of the unmodulated electromagnetic signalreceived during the noise detection portion of the detection cycle.

The interrogation and detection system may adjust the signal detectionthreshold by adjusting the signal detection threshold based at least inpart on a first number of determined noise values indicative of a noiselevel during at least one noise detection portion that occurred beforethe receive response portion of a first one of the detection cycles anda second number of determined noise values indicative of a noise levelduring at least one noise detection portion that occurred after thereceive response portion of the first one of the detection cycles.

The interrogation and detection system may adjust the signal detectionthreshold based at least in part on the determined noise value of atleast one of the detection cycles by adjusting the signal detectionthreshold to be approximately twice an average of at least one of thefirst and the second number of determined noise values.

The interrogation and detection system may adjust the signal detectionthreshold based at least in part on the determined noise value of atleast one of the detection cycles by adjusting the signal detectionthreshold to be approximately twice a greatest one of at least one ofthe first and the second number of determined noise values.

The interrogation and detection system may determine the presence orabsence of a transponder by comparing a maximum value of a plurality ofmatched filter outputs with the adjusted signal threshold.

The interrogation and detection system may adjust the signal detectionthreshold based at least in part on the determined noise value of atleast one of the detection cycles by adjusting the signal detectionthreshold to be approximately twice the determined noise value.

The interrogation and detection system may adjust the signal detectionthreshold based at least in part on the determined noise value of atleast one of the detection cycles includes adjusting the signaldetection threshold to be the larger of approximately twice thedetermined noise value or a defined threshold value. The definedthreshold value may for example be approximately 0.5 mV.

In some implementations, the interrogation and detection systemdetermines if an output of at least one matched filter during the noisedetection portion of the detection cycle exceeds a noise fault thresholdindicative of a noise fault.

In some implementations, the interrogation and detection systemdetermines if the output of the at least one matched filter during thenoise detection portion of the detection cycle exceeds the noise faultthreshold for a defined period of time. The interrogation and detectionsystem may terminate the detection cycle in response to the output ofthe at least one matched filter exceeding the noise fault threshold forthe defined period of time.

The interrogation and detection system may convert the receivedsignal(s) from the time domain to the frequency domain spectrum. Theinterrogation and detection system may, for example, perform a Fouriertransform, for instance a fast Fourier transform such as a 256 pointfast Fourier transform. Suitable algorithms and/or sets of software codefor performing such are available or can be written.

The interrogation and detection system may search the frequency domainspectrum to determine the object with the strongest resonance in adefined frequency band. For example, the interrogation and detectionsystem may search the frequency domain spectrum from about 120 kHz toabout 175 kHz. An amplitude of the resonant object may be computed asthe sum of the resonant power plus and minus 2 fast Fourier transformbins from the peak resonance frequency. This approach may provide a moreaccurate measurement of power than simply using the peak value. Thefrequency of the resonant object may be computed using an interpolationapproach. This approach may provide a more accurate determination ofresonant frequency than simply using the fast Fourier bin number.

The interrogation and detection system may determine the presence orabsence of a transponder based at least in part on a frequency of theunmodulated electromagnetic signals received during the detection cyclebeing within a defined frequency range. The defined frequency range mayextend from about 137 kHz to about 160 kHz, for example.

The interrogation and detection system may determine a Q value (i.e.,Quality factor) of the resonant object from a signal decay slope for thereceived unmodulated electromagnetic signal(s) returned by the resonantobject. The interrogation and detection system may, for example, usemultiple windows, for instance five (5) window positions may providesuitable results.

The interrogation and detection system may determine the presence orabsence of a transponder based at least in part on a Q value of theunmodulated electromagnetic signal(s) received during the detectioncycle. The interrogation and detection system may preferably employ theQ value determination in conjunction with determination based on thefrequency and on the determination based on the adjusted signaldetection threshold.

In some implementations, the interrogation and detection systemdetermines the presence or absence of a transponder is based at least inpart on a Q value of the unmodulated electromagnetic signals receivedduring the detection cycle being at least equal to a threshold Q value.The threshold Q value may be 35, for example. The interrogation anddetection system may preferably employ the Q value determination inconjunction with determination based on the frequency and on thedetermination based on the adjusted signal detection threshold.

Consequently, tag detection may advantageously be based on the receivedunmodulated electromagnetic signal(s) satisfying all threeconditions: 1) measured amplitude is above a threshold, which may be anadjustable threshold, 2) measured frequency is between a lower limit andan upper limit, and 3) measured Q value is above a minimum Q threshold.Interference, for example from RFID tags or EKG cables, are rejectedwhen any of the following three conditions are satisfied: a) measuredfrequency is below the lower frequency limit, b) measured frequency isabove the upper frequency limit, or c) measured Q value is below thethreshold Q value. Such may provide significantly superior results overprevious approaches, preventing false positives which could otherwisecause a patient to remain open for longer period of time during surgeryand tie up hospital personnel and resources.

FIG. 9 shows a graph 900 of a simulated transponder response signal 902and a noise signal 904. The inexpensive transponders usable withimplementations disclosed herein typically have a relatively largevariation in the frequency of signals they emit, making it difficult toaccurately detect the signals returned by the transponders. This may beparticularly difficult in some environments which are noisy with respectto the particular resonant frequencies of the transponders. For example,operating rooms may have one or more electronic medical devices thatemit RF noise that is harmonically synchronous with the response signalsreceived from the transponders. Consequently, even though the responsessignals may be received synchronously with the transmitted interrogationsignals, noise that is harmonically synchronous with the responsesignals may still be high if the peaks of the noise occur at times theinterrogation and detection system is expecting to see response signalsfrom a transponder.

The transponder response signal 902 may, for example, be a nominalperiodic signal centered around a particular frequency (e.g., 136 kHz,145 kHz, 154 kHz, etc.). The noise signal 904 may be emitted from anelectronic medical device located proximate to the interrogation anddetection system 104 (FIGS. 1A-1B), for example. In this illustration,the amplitude of the noise signal 904 is much greater than the amplitudeof the transponder response signal 902. As shown, at a point 906 in timethe noise signal 904 is at a peak and the transponder response signal902 is near its zero crossing. If the interrogation and detection system104 were to obtain a sample at the point 906 the noise signal 904 wouldmask the transponder response signal 902. Conversely, at points 908 and910, the noise signal 904 is at or close to its zero crossing while thetransponder response signal 902 is near its peak. If the interrogationand detection system 104 can sample the simulated response signal 902 attimes when the noise signal 904 is at its zero crossing or at a lowamplitude, it is possible for the interrogation and detection system todetect a transponder through the noise signal 904 (or “noise floor”)that is many times greater than the transponder response signal 902.

To accomplish this, in some implementations the scanning process foreach antenna or coil is broken down into N_(SS) subsample scan cyclesfor each transmit frequency. Each of the subsample scan cycles includesone or more interrogation cycles. As discussed in further detail below,each of the interrogation cycles in a particular one of the N_(SS)subsample scan cycles is shifted forward in time a fraction of theperiod (T) of a nominal expected transponder response signal 902 toprovide N_(SS) opportunities to avoid harmonic noise being synchronousin time with the desired transponder response signal.

FIG. 10 illustrates timing for a single interrogation cycle 1010 in animplementation that utilizes the aforementioned subsample scan cycles,according to one illustrated implementation. Each of the N_(SS)subsample scan cycles may include one or more interrogation cycles 1010,as discussed below. The custom logic in the FPGA 508 (FIG. 5) generatesthe timing and control signals for each interrogation cycle 1010. Duringa transmit portion 1010 a of the interrogation cycle 1010, the logic ofthe FPGA 508 drives transistor control lines to generate the transmitsignal. The FPGA logic controls the frequency of the transmit signal. Insome implementations, the transmit portion 1010 a has a duration of 200microseconds (μs), for example. During a dump portion 1010 b of theinterrogation cycle 1010, the logic of the FPGA 508 drives a gate of adump TRIAC to quickly drain the transmit energy from the antenna toallow detection of the response signal from the transponder 116, if any.In some implementations, the dump portion 1010 b has a duration of 10μs, for example. A recovery portion 1010 c of the interrogation cycle1010 allows receive filters and amplifiers to recover from thetransmitted signal before detecting the response signal from thetransponder 116, if any. The recovery portion 1010 c may have a durationof 100 μs, for example. During a receive response portion 1010 d of theinterrogation cycle 1010, the FPGA 508 controls the signal ADC 128 tosample the response signal from the transponder 116, if any. The signalADC 128 may, for example, sample at a 1 MHz sample rate (i.e., 1 sampleper μs) with a 12-bit resolution. In some implementations, the receiveresponse portion 1010 d has a duration of 512 μs, such that the signalADC 128 obtains 512 measurements at the 1 MHz sample rate during thereceive response portion 1010 d. A skip portion 1010 e of theinterrogation cycle 1010 may be provided during which time measurementsfrom the signal ADC 128 are skipped or ignored. In some implementations,the skip portion 1010 e has a duration of 40 μs. The timing of thereceive response portion 1010 d may be such that the transponderresponse signal is synchronous to the transmit time.

A subsample scan cycle delay period 1010 f of the interrogation cycle1010 has a unique duration for interrogation cycles associated with aparticular one of the N_(SS) subsample scan cycles. Interrogation cyclesassociated with different ones of the N_(SS) subsample scan cycles mayhave subsample scan cycle delay periods 1010 f having differingdurations. In some implementations, the subsample scan cycle delayperiod 1010 f associated with respective ones of the N_(SS) subsamplescan cycles may be approximately a fraction of the period (T) of theexpected transponder response signal 902 (FIG. 9). For example, thesubsample scan cycle delay periods 1010 f for interrogation cyclesassociated with subsample scan cycles 1 to N_(SS) may be approximately:

(0/N_(SS))*T for interrogation cycles of subsample scan cycle 1;

(1/N_(SS))*T for interrogation cycles of subsample scan cycle 2;

(2/N_(SS))*T for interrogation cycles of subsample scan cycle 3;

. . .

((N_(SS)−1)/N_(SS))*T for interrogation cycles of subsample scan cycleN_(SS).

Thus, the period (T) of the expected transponder response signal isdivided into N_(SS) start times, with each of the N_(SS) subsample scancycles being associated with a different one of the start times.

FIG. 11A is a timing diagram 1100 illustrating an overall instrumentscan cycle 1102, according to one illustrated implementation. Theinstrument scan cycle 1102 may be implemented by the interrogation anddetection system 104 to scan for one or more resonant transponders. Theinstrument scan cycle 1102 may have a duration between a start time anda stop time that is less than about 20 seconds (e.g., two seconds, fiveseconds, 10 seconds, 15 seconds, etc.) so that the user operating theinterrogation and detection system 104 does not need to wait an extendedperiod of time to perform a scan operation. The instrument scan cycle1102 may be executed one or more times during the Scan Mode of theinterrogation and detection system 104. As discussed in further detailbelow, each instrument scan cycle 1102 may include one or more coil scancycles, which may include one or more frequency specific sample cycles,which may include one or more subsample scan cycles, which may includeone or more interrogation cycles.

The instrument scan cycle 1102 includes a number N_(COILS) of coil scancycles 1104, one coil scan cycle for each of N_(COILS) present in theinterrogation and detection system 104. For example, the detectionsystem 104 may include three antenna coils (N_(COILS)=3), mutuallyorthogonal to each other, such that each instrument scan cycle 1102includes three coil scan cycles 1104. In some implementations thedetection system 104 may include six antenna coils (N_(COILS)=6), or agreater or fewer number of antenna coils. In some implementations, thedetection system 104 includes a single coil (N_(COILS)=1), such thatonly a single coil scan cycle 1104 is performed during each instrumentscan cycle 1102.

FIG. 11B is a timing diagram 1106 illustrating a cycle for one of thecoil scan cycles 1104 shown in FIG. 11A, according to one illustratedimplementation. The coil scan cycle 1104 includes a number N_(FREQ) offrequency specific sample cycles 1108, one for each transmit frequencyto be used by the interrogation and detection system 104. The numberN_(FREQ) of frequency specific sample cycles 1108 may be any suitablevalue, such as one, two, five, eight, etc. For example, in someimplementations the interrogation and detection system 104 may transmitinterrogation signals at 139 kHz, 145 kHz, and 154 kHz during frequencyspecific sample cycle 1, frequency specific sample cycle 2, andfrequency specific sample cycle 3, respectively. In someimplementations, the interrogation and detection system 104 may transmitat a single frequency, such that only a single frequency specific samplecycle 1108 is performed during each coil scan cycle 1104.

FIG. 11C is a timing diagram 1110 illustrating a cycle for one of thefrequency specific sample cycle 1108, according to one illustratedimplementation. The frequency specific sample cycle 1108 includes anumber N_(SS) of subsample scan cycles 1112, one for each subsample tobe collected by the interrogation and detection system 104. As usedherein, a subsample may refer to measurements obtained during asubsample scan cycle. As discussed above, the number N_(SS) of subsamplescan cycles 1112 in each frequency specific sample cycle may be anysuitable value, such as two, five, 10, 15, etc. As discussed above, eachof the N_(SS) subsample scan cycles has a unique subsample scan cycledelay period associated therewith. The subsample scan cycle delayperiods for each of the N_(SS) subsample scan cycles are applied duringrespective interrogation cycles associated with the respective subsamplescan cycles.

FIG. 11D is a timing diagram 1114 illustrating one cycle of one of thesubsample scan cycles 1112, according to one illustrated implementation.The subsample scan cycle 1112 includes a number N_(I) of interrogationcycles 1010 (FIG. 10). As discussed below with reference to the exampleshown in FIG. 12, each of the N_(I) interrogation cycles 1010 has asubsample scan cycle delay period 1010 f associated with one of theparticular subsample scan cycles 1112. In other words, interrogationcycles 1 to N_(I) for one of the subsample scan cycles 1112 all have thesame subsample scan cycle delay period 1010 f. The number ofinterrogation cycles (N_(I)) per subsample scan cycle 1112 may be anysuitable value, such as 10, 250, 500, or 1000 interrogation cycles persubsample scan cycle.

FIG. 12 illustrates a timing diagram 1200 for performing N_(SS)subsample scan cycles 1202 (labeled subsample scan cycles 1-7) to obtainN_(SS) subsamples, where N_(SS) equals seven in this illustratedexample. In this implementation, each of the subsample scan cycles 1-7include 250 interrogation cycles 1010 (FIG. 10). Each of theinterrogation cycles is designated as I_(X-Y), where X is the subsamplescan cycle with which the interrogation cycle is associated and Y is thenumber of the interrogation cycle within the subsample scan cycle. Forexample, I₂₋₃ represents the third interrogation cycle 1010 in subsamplescan cycle 2. During a particular frequency specific sample cycle 1108(FIG. 11) of a coil scan cycle 1104, the interrogation and detectionsystem 104 performs subsample scan cycles 1-7 using a particular antennacoil (e.g., coil 338 a of FIG. 3D) by sequentially executinginterrogation cycles I₁₋₁ to I₁₋₂₅₀, I₂₋₁ to I₂₋₂₅₀, I₃₋₁ to I₃₋₂₅₀,I₄₋₁ to I₄₋₂₅₀, I₅₋₁ to I₅₋₂₅₀, I₆₋₁ to I₆₋₂₅₀, and I₇₋₁ to I₇₋₂₅₀, fora total of 1750 interrogation cycles, in this implementation. Table 2below shows the approximate subsample scan cycle delay periods 1010 ffor interrogation cycles 1010 within each of the subsample scan cycles1-7.

TABLE 2 Subsample Scan Cycle Subsample Scan Cycle Delay Period for DelayPeriod: Response Subsample Scan Interrogation Cycles in Signal at 145kHz Cycle Subsample Scan Cycle (T = 6.9 μs) 1 (0/7) * T   0 μs 2 (1/7) *T ~1 μs 3 (2/7) * T ~2 μs 4 (3/7) * T ~3 μs 5 (4/7) * T ~4 μs 6 (5/7) *T ~5 μs 7 (6/7) * T ~6 μs

In the illustrated implementation, the subsample scan cycle delayperiods 1010 f are evenly spaced across the duration of the period (T)of the expected transponder response signal. For example, for atransponder response signal expected to have a center frequency of about145 kHz, the period T is approximately 6.9 μs. Accordingly,interrogation cycles of a next successive subsample scan cycle has asubsample scan cycle delay period 1010 f that is about 1/7 of thetransponder response signal period T greater than interrogation cyclesof a previous successive subsample scan cycle. As an example, thesubsample scan cycle delay period 1010 f for interrogation cycles I₄₋₁to I₄₋₂₅₀ of subsample scan cycle 4 is three (3) μs and the subsamplescan cycle delay period 1010 f for interrogation cycles I₅₋₁ to I₅₋₂₅₀of subsample scan cycle 5 is four (4) μs. By utilizing seven differentsubsample scan cycle delay periods 1010 f spread across the duration ofthe period T of the expected transponder response signal, theprobability of a sampling at a time of low harmonically synchronousnoise and high transponder response signal is increased. In someimplementations, more or less than seven subsample scan cycles may beused.

In some implementations, the subsample scan cycle delay periods 1010 fof the interrogation cycles may be different fractions of the period (T)of the expected transponder response signal, offset by one or moreperiods T. For example, in some implementations with four subsample scancycles, interrogation cycles of a subsample scan cycle 1 may have asubsample scan cycle delay period of T (i.e., (0/4)*T+T), such that thesubsample scan cycle delay period is offset by one period T relative tothe example provided in Table 2. Similarly, interrogation cycles of asubsample scan cycle 2 may have a subsample scan cycle delay period of(5/4)*T (i.e., (1/4)*T+T=(5/4)*T), interrogation cycles of a subsamplescan cycle 3 may have a subsample scan cycle delay period of (6/4)*T(i.e., (2/4)*T+T=(6/4)*T), and interrogation cycles of a subsample scancycle 4 may have a subsample scan cycle delay period of (7/4)*T (i.e.,(3/4)*T+T=(7/4)*T). Importantly, the subsample scan cycle delay periodsfor the interrogation cycles in respective subsample scan cycles aredifferent fractions of the expected transponder response signal. Othervalues for the subsample scan cycle delay periods may be used to obtainsamples at different start times within the period T of the expectedtransponder response signal.

FIG. 13 shows a method 1300 of operating an interrogation and detectionsystem to implement a coil scan cycle 1104 (FIGS. 11A-11D), according toone illustrated implementation. The method 1300 may be implemented byany of the interrogation and detection system implementations discussedabove. The method 1300 may be used to collect subsamples using thesubsample scan cycles including the interrogation cycles 1010illustrated in FIGS. 10 and 12 for a single antenna coil. The method1300 may be repeated for interrogation and detection systems utilizing aplurality of antenna coils (e.g., two sets of three mutually orthogonalantenna coils).

The method starts at 1302. The method 1300 may, for example, start whenan interrogation and detection system enters the Scan Mode 714 (FIG. 7).At 1304, the interrogation and detection system initializes a controlvariable FREQUENCY_COUNT that may be used for comparison with a numberof frequency bands to be used in the coil scan cycle (i.e., the numberof frequency specific sample cycles 1108). In some implementations, morethan one frequency band may be used during the coil scan cycle. Forexample, a first interrogation signal may be centered around 139 kHz, asecond interrogation signal may be centered around 145 kHz, and a thirdinterrogation signal may be centered around 154 kHz, for a total ofthree frequency specific sample cycles. Other center channels orfrequencies may for example be 136 kHz, 142 kHz, 148 kHz, and or 151kHz, or any other frequency suitable for exciting the transponder toresonate.

At 1306, the interrogation and detection system initializes a controlvariable SUBSAMPLE_COUNT. This control variable may be used during themethod 1300 for comparison with a number of subsample scan cycles N_(SS)to be executed by the interrogation and detection system. In the exampleshown in FIG. 12, the number of subsample scan cycles N_(SS) is seven,but more or less subsample scan cycles may be used depending on how manydivisions or start times in the period T of the expected transponderresponse signal are to be used. If N_(SS) is relatively small, theprobability of sampling at a time of low harmonically synchronous noiseis reduced since the number of opportunities is reduced. If N_(SS) isrelatively large, the probability of sampling at a time of lowharmonically synchronous noise is increased, but a tradeoff is that thetotal time for the coil scan cycle 1104 may also be increased.

At 1308, the interrogation and detection system initializes a controlvariable INTERROGATION_COUNT. This control variable may be used duringthe method 1300 for comparison with the number N_(I) of interrogationcycles 1010 in each subsample scan cycle. In the example of FIG. 12,each subsample scan cycle includes 250 interrogation cycles 1010. Moreor less interrogation cycles per subsample scan cycle may be used.

At 1310, the interrogation and detection system begins a firstinterrogation cycle (interrogation cycle 1) for a first subsample scancycle (subsample scan cycle 1) by emitting an electromagneticinterrogation signal centered at first frequency (frequency specificsample cycle 1) during a transmit portion 1010 a of the interrogationcycle (see FIGS. 10 and 11). At 1312, the interrogation and detectionsystem receives unmodulated electromagnetic signals during a receiveresponse portion 1010 d of the interrogation cycle that follows thetransmit portion 1010 a of the interrogation cycle. As discussed abovewith reference to FIG. 10, the interrogation cycle may include a dumpportion 1010 b, recovery portion 1010 c, and/or a skip portion 1010 ebetween the transmit portion 1010 a and the receive response portion1010 d. The timing of the receive response portion 1010 d may be suchthat the expected transponder response signal is synchronous or coherentwith the transmit portion 1010 a to improve the likelihood that peaks ofthe transponder response signal are detected. During the receiveresponse portion 1010 d of the interrogation cycle, the FPGA 508controls the signal ADC 128 to sample the response signal from thetransponder. The signal ADC 128 may, for example, obtain 512measurements in 512 μs by sampling at a 1 MHz sample rate (i.e., 1sample per μs). In some implementations the signal ADC 128 may sample atdifferent rates and may obtain more or less measurements during eachreceive response portion 1010 d.

At 1314, the interrogation and detection system waits a subsample scancycle delay period 1010 f, which in some implementations is a fractionof the period T of the expected transponder response signal, beforestarting the next interrogation cycle at 1310. The subsample scan cycledelay period may be approximately equal to ((SUBSAMPLE_COUNT−1)/N_(SS))times the period (T) of the expected transponder response signal, insome implementations. Thus, for interrogation cycles associated withsubsample scan cycle 1, the subsample scan cycle delay period isapproximately zero seconds (i.e., (0/N_(SS))*T=0). For interrogationcycles associated with subsample scan cycle 2, the subsample scan cycledelay period is approximately equal to (1/N_(SS))*T, and so on asdiscussed above.

At 1316, the interrogation and detection system increments the controlvariable INTERROGATION_COUNT. At 1318, the interrogation and detectionsystem compares the value of INTERROGATION_COUNT to the number ofinterrogation cycles N_(I) per subsample scan cycle. The interrogationand detection system thus continues to loop through acts 1310-1314(i.e., interrogation cycles) until all of the interrogation cycles insubsample scan cycle 1 have been executed. The number of interrogationcycles per subsample scan cycle may be any suitable value, such as 1,100, 250, 500, 2000, etc.

Once all of the interrogation cycles for subsample scan cycle 1 havebeen executed (i.e., decision 1318=YES), the interrogation and detectionsystem increments the control variable SUBSAMPLE_COUNT at 1320, andcompares its value to the number of subsample scan cycles N_(SS) at1322. Thus, similar to the acts for subsample scan cycle 1, theinterrogation and detection system executes the acts 1310-1314 forsubsample scan cycle 2 to subsample scan cycle N_(SS) to complete atotal of N_(SS) subsample scan cycles and collect N_(SS) subsamples.

Once all of the interrogation cycles for each of the subsample scancycles 1 to N_(SS) have been executed (i.e., decision 1322=YES), theinterrogation and detection system increments the control variableFREQUENCY_COUNT at 1324 and compares its value to the number of transmitfrequencies (N_(FREQ)) at 1326. If the number of transmit frequenciesN_(FREQ) is greater than one, the interrogation and detection systemrepeats the acts discussed above to perform N_(SS) subsample scan cyclesat each of the number N_(FREQ) of transmit frequencies for a total ofN_(FREQ) frequency specific sample cycles.

The method 1300 may terminate at 1328 until started again. As discussedabove, the method 1300 may repeat for one or more additional antennacoils of the interrogation and detection system. The method 1300 maycontinually repeat when the interrogation and detection system is in theScan Mode. Alternatively or additionally, the method 1300 may runconcurrently with other methods or processes.

FIG. 14 shows a method 1400 of operating an interrogation and detectionsystem to execute an instrument scan cycle 1102 (FIG. 11), according toone illustrated implementation. The method 1400 may be implemented byany of the interrogation and detection system implementations discussedabove. The method 1400 may be used to collect subsamples by performingsubsample scan cycles using the interrogation cycles illustrated inFIGS. 10 and 12.

The method starts at 1402. The method 1400 may, for example, start whenan interrogation and detection system enters the Scan Mode 714 (FIG. 7).At 1404, the interrogation and detection system initializes a controlvariable COIL_COUNT. This control variable may be used during the method1400 for comparison with a number of coils (N_(COILS)) included in theinterrogation and detection system. For example, in some implementationsthe interrogation and detection system may include a plurality of coilsor antennas that may be used to scan for transponders. In someimplementations, the interrogation and detection system may include aplurality of coils spaced apart from each other that are each designedto detect transponders in different physical locations. For example, insome implementations six coils may be spaced apart in or on a matpositioned under a patient on a patient support structure. The six coilsmay be used to detect transponders at different locations proximate tothe patient's body. In some implementations, multiple coils may beprovided to transmit or receive signals in multiple directions (e.g.,x-, y-, and z-directions).

At 1406, the interrogation and detection system performs a coil scancycle 1104 (FIG. 11A) to detect transponders using a first coil. Theinterrogation and detection system may execute this act using the method1300 of FIG. 13 discussed above to perform a coil scan cycle 1104, whichmay include N_(FREQ) frequency specific sample cycles, each of which mayinclude N_(SS) subsample scan cycles, each of which may include N_(I)interrogation cycles. At 1408, the interrogation and detection systemincrements the control variable COIL_COUNT and compares its value to thenumber of coils at 1410. If the interrogation and detection subsystemincludes additional coils, the system sequentially performs coil scancycles 1104 in round robin fashion for each of the coils to scan fortransponders.

The method 1400 may terminate at 1412 until started again. The method1400 may continually repeat when the interrogation and detection systemis in the Scan Mode. Alternatively or additionally, the method 1400 mayrun concurrently with other methods or processes.

FIG. 15 shows a method 1500 of operating an interrogation and detectionsystem to execute one or more instrument scan cycles 1102 (FIG. 11),according to one illustrated implementation. The method 1500 may beimplemented by any of the interrogation and detection systemimplementations discussed above. The method 1500 may be used to collectsubsamples by performing subsample scan cycles using the interrogationcycles illustrated in FIGS. 10 and 12.

The method 1500 begins at 1502. At 1504 the interrogation and detectionsystem may receive a scan mode selection from a user (e.g., via thecontroller 110). In some implementations, a graphical user interface ofthe controller 110 may present a prompt to the user requesting aselection of a scan mode. In some implementations, the system mayautomatically select a scan mode for the user. In this implementation,the interrogation and detection system is configured to provide at leasttwo different types of instrument scan cycles: a static scan and adynamic scan. During a static scan, the user maintains the probe 112 ina substantially fixed position relative to the patient 108. For example,in a child delivery medical setting, the user may position the probe 112near the top of the patient's pelvic bone when the patient is in thelithotomy position to scan for detection of objects (e.g., retainedsponges). During a dynamic scan, the user may move the probe 112 tovarious locations to scan for detection of objects. For example, in thedynamic instrument scan cycle mode, the user may move the probe 112 neara trash can, near portions of the patient's body, near a drape bag,and/or near other areas in a medical facility to scan for objects (e.g.,so that such objects may be counted).

If the user has selected a static scan (i.e., decision 1506=YES), theinterrogation and detection system executes one or more staticinstrument scan cycles at 1508. If the user has selected a dynamic scan(i.e., decision 1510=YES), the interrogation and detection systemexecutes one or more dynamic instrument scan cycles at 1512.

The static instrument scan cycle and the dynamic instrument scan cyclediffer by the number of subsamples obtained. The time available for thedynamic instrument scan cycle is less than the time available for thestatic instrument cycle because, in the dynamic scan cycle mode, theuser is constantly moving the probe 112 relative to a transponder thatis to be detected. Thus, to provide a relatively fast scan, in someimplementations only a single frequency specific sample cycle 1108(FIGS. 11B and 11C) with four subsample scan cycles 1112 (FIGS. 11C and11D) are executed in the dynamic instrument scan cycle mode. This is incontrast to the static instrument scan cycle, which in someimplementations utilizes two or more frequency specific sample cycles1108 and seven or more subsample scan cycles 1112 per frequency specificsample cycle.

In operation, the medical provider 102 may operate the interrogation anddetection system in both instrument scan cycle modes after a medicalprocedure. For example, the user may operate the interrogation anddetection system in the static scan cycle mode to first detect whetherany objects are retained in the patient, and then operate the system inthe dynamic scan cycle mode to detect whether any objects are located insurrounding areas (e.g., trash cans, drape bags, etc.).

As discussed above, in some implementations the dynamic scan modeincludes a single frequency specific sample cycle 1108 (FIGS. 11B and11C) that includes four subsample scan cycles 1112. Thus, the instrumentscan cycle 1102 in the dynamic mode includes sequentially performing acoil scan cycle 1104 (FIG. 11A) for each of the three orthogonal coils338 a, 338 b, and 338 c, where each coil scan cycle includes onefrequency specific sample cycle 1108 that includes four subsample scancycles 1112.

In some implementations, the static scan mode includes two frequencyspecific sample cycles 1108 that each include seven subsample scancycles 1112. Thus, the instrument scan cycle 1102 in the static modeincludes sequentially performing a coil scan cycle 1104 for each of thethree orthogonal coils 338 a, 338 b, 338 c of the two coil sets, whereeach coil scan cycle includes two frequency specific sample cycles 1108that each include seven subsample scan cycles 1112.

In some implementations, a single subsample scan cycle 1112 may have aduration of approximately 216 milliseconds. Continuing with the examplediscussed above, a single dynamic instrument scan cycle may have aduration of about 2.6 seconds (i.e., 216 milliseconds per subsample scancycle, 4 subsample scan cycles per frequency specific sample scan, 1frequency specific sample scan per coil, and 3 orthogonal coils). Asingle static instrument scan cycle may have a duration of approximately9.1 seconds (i.e., 216 milliseconds per subsample scan cycle, 7subsample scan cycles per frequency specific sample scan, 2 frequencyspecific sample scans per coil, and 3 orthogonal coils). The durationsof the static and dynamic instrument scan cycles may be modified to suita particular application, recognizing the tradeoff between scan time andthe number of samples collected.

The method 1500 terminates at 1514 until started again. The method 1500may start again, for example, when the user makes a selection of one ofthe dynamic scan cycle mode or the static scan cycle mode.

FIG. 16 shows a method 1600 of operating an interrogation and detectionsystem, according to one illustrated implementation.

At 1602, the interrogation and detection system determines the presenceor absence of a transponder based at least in part on at least one ofthe subsamples obtained by performing the method 1300 and/or the method1400 discussed above (FIGS. 13 and 14).

As discussed above, the signal ADC 128 (FIG. 5) converts the signalreceived from the transponder, if any, from analog to digital. Suchconversion may, for example, be performed at a sampling rate of 1 MHzwith a 12-bit data resolution. In the example shown in FIG. 12,subsample scan cycles 1-7 each include 250 interrogation cycles, and thesignal ADC 128 obtains 512 measurements per interrogation cycle. Thesampled ADC data for each subsample scan cycle may be accumulatedtogether or integrated to compute the total summed response signalreceived from the transponder 116, if any, for each subsample.

In some implementations, the accumulated or integrated received signalfor each subsample is matched filtered with both in-phase and quadraturereference signals to determine the signal magnitude. The receivedresponse signal may be matched filtered with a plurality of referencesignals, for example with the seven reference signals, for instance asshown in Table 1 above. Some implementations may employ matchedfiltering before accumulating or integrating the received signal.

For each subsample collected, the maximum value for the matched filters(e.g., seven matched filters) with active transmit may be compared withan adjusted detection threshold. If the maximum value is greater thanthe detection threshold for one or more subsamples, then a responsesignal from a transponder is considered as having been detected, andappropriate action is taken, such as discussed above with reference toFIG. 7. In some implementations, a value greater than the detectionthreshold for two or more subsamples is required before a transponder isconsidered to have been detected.

The above description of illustrated implementations, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe implementations to the precise forms disclosed. Although specificimplementations of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious implementations can be applied to other transponders andinterrogation and detection systems, not necessarily the exemplarysurgical object transponders and interrogation and detection systemsgenerally described above.

For instance, the foregoing detailed description has set forth variousimplementations of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one implementation, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that theimplementations disclosed herein, in whole or in part, can beequivalently implemented in standard integrated circuits, as one or morecomputer programs running on one or more computers (e.g., as one or moreprograms running on one or more computer systems), as one or moreprograms running on one or more controllers (e.g., microcontrollers) asone or more programs running on one or more processors (e.g.,microprocessors), as firmware, or as virtually any combination thereof,and that designing the circuitry and/or writing the code for thesoftware and or firmware would be well within the skill of one ofordinary skill in the art in light of this disclosure.

In addition, those skilled in the art will appreciate that themechanisms of taught herein are capable of being distributed as aprogram product in a variety of forms, and that an illustrativeimplementation applies equally regardless of the particular type ofsignal bearing media used to actually carry out the distribution.Examples of signal bearing media include, but are not limited to, thefollowing: recordable type media such as floppy disks, hard disk drives,CD ROMs, digital tape, and computer memory; and transmission type mediasuch as digital and analog communication links using TDM or IP basedcommunication links (e.g., packet links).

The various implementations described above can be combined to providefurther implementations. U.S. Provisional Patent Application Ser. No.61/056,787, filed May 28, 2008; U.S. Provisional Patent Application Ser.No. 61/091,667, filed Aug. 25, 2008; U.S. Provisional Patent ApplicationNo. 60/811,376 filed Jun. 6, 2006; U.S. Pat. No. 6,026,818, issued Feb.22, 2000; U.S. Patent Publication No. US 2004/0250819, published Dec.16, 2004; U.S. provisional patent application Ser. No. 60/811,376, filedJun. 6, 2006; U.S. non-provisional patent application Ser. No.11/743,104, filed May 1, 2007; U.S. provisional patent application Ser.No. 61/972,826, filed Mar. 31, 2014; U.S. provisional patent applicationSer. No. 61/972,832, filed Mar. 31, 2014; U.S. non-provisional patentapplication Ser. No. 14/327,208, filed Jul. 9, 2014; and U.S.non-provisional patent application Ser. No. 14/327,208, filed Jul. 9,2014, and international PCT patent application Serial No. US2014/070547,filed Dec. 16, 2014, are incorporated herein by reference, in theirentirety. Aspects of the implementations can be modified, if necessary,to employ systems, circuits and concepts of the various patents,applications and publications to provide yet further implementations.

These and other changes can be made to the implementations in light ofthe above-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificimplementations disclosed in the specification and the claims, butshould be construed to include all possible implementations along withthe full scope of equivalents to which such claims are entitled.Accordingly, the claims are not limited by the disclosure.

1. A transponder detection device to detect surgical objects in a workarea, the surgical objects marked by respective resonant tag elementsthat produce return signals in response to energization, the transponderdetection device comprising: a hand-held probe comprising: a housinghaving a cavity therein; and a first coil assembly and a second coilassembly received within the cavity of the housing spaced from eachother, wherein each of the first and the second coil assembliesrespectively includes: a substantially spherically shaped coil form thatincludes three coil support channels, each of the three coil supportchannels which define an outer coil support surface; a first antennaelement comprising a first electrical conductor wound around the outercoil support surface of a first one of the three coil support channels,the first antenna element arranged to transmit and receive signalsgenerally in a first coordinate direction; a second antenna elementcomprising a second electrical conductor wound around the outer coilsupport surface of a second one of the three coil support channels overthe first electrical conductor, the second antenna element arranged totransmit and receive signals generally in a second coordinate directionorthogonal to the first coordinate direction; and a third antennaelement comprising a third electrical conductor wound around the outercoil support surface of a third one of the three coil support channelsover the first electrical conductor and the second electrical conductor,the third antenna element arranged to transmit and receive signalsgenerally in a third coordinate direction orthogonal to the firstcoordinate direction and the second coordinate direction.
 2. Thetransponder detection device of claim 1 wherein the cavity of thehousing is defined by a first body portion that receives the first coilassembly, a second body portion that receives the second coil assembly,and a handle portion disposed between the first body portion and thesecond body portion.
 3. The transponder detection device of claim 2wherein the handle portion is disposed between the first body portionand the second body portion to allow the first body portion and thesecond body portion to at least partially surround a human joint duringuse.
 4. The transponder detection device of claim 1 wherein at least oneof the first, the second or the third antenna elements of the first coilassembly is arranged to transmit and receive signals generally in acoordinate direction which is the same as a coordinate direction inwhich at least one of the first, the second or the third antennaelements of the second coil assembly is arranged to transmit and receivesignals.
 5. The transponder detection device of claim 1 wherein each ofthe first, the second and the third antenna elements of the first coilassembly is arranged to transmit and receive signals generally in acoordinate direction which is the same as a coordinate direction inwhich a different one of the first, the second or the third antennaelements of the second coil assembly is arranged to transmit and receivesignals.
 6. The transponder detection device of claim 1 wherein at leastone of the first, the second or the third antenna elements of the firstcoil assembly is coplanar with at least one of the first, the second orthe third antenna elements of the second coil assembly.
 7. Thetransponder detection device of claim 1 wherein, for each of therespective coil forms of the first and the second coil assemblies, eachof the three coil support channels is shaped as a spherical zone of avirtual sphere.
 8. The transponder detection device of claim 7 wherein,for each of the respective coil forms of the first and the second coilassemblies, each of the three coil support channels is shaped as aspherical zone of a virtual sphere centered on a great circle of thevirtual sphere.
 9. The transponder detection device of claim 1 wherein,for each of the respective coil forms of the first and the second coilassemblies, the three coil support channels are shaped as a sphericalzone of the substantially spherically shaped coil form centered onrespective orthogonal great circles of the coil form.
 10. Thetransponder detection device of claim 1, further comprising: a lightsource coupled to the housing that provides a visual indication of atleast a status of the transponder detection device.
 11. The transponderdetection device of claim 1, further comprising: a processor operativelycoupled to the respective first antenna elements, the second antennaelements, and the third antenna elements of the first and the secondcoil assemblies; and a nontransitory processor-readable mediumcommunicatively coupled to the processor and that stores at least one ofinstructions or data executable by the processor, which cause theprocessor to: control each of the first antenna elements, the secondantenna elements and the third antenna elements of the first and thesecond coil assemblies to emit wideband interrogation signals; receiveany of the return signals from any of the resonant tag elements; anddetermine from a receipt of any of the return signals whether any of theresonant tag elements are present in the work area.
 12. The transponderdetection device of claim 11 wherein the processor: controls each of therespective first antenna elements, the second antenna elements and thethird antenna elements of the first and the second coil assemblies toemit wideband interrogation signals in time-wise succession during atransmit portion of respective transmit and receive cycles, and controlseach of the first antenna elements, the second antenna elements and thethird antenna elements of the first and the second coil assemblies tonot emit wideband interrogation signals during a receive portion ofrespective transmit and receive cycles.
 13. The transponder detectiondevice of claim 11 wherein the processor further: receives a selectionof at least one of a dynamic scan mode and a static scan mode; inresponse to receiving a selection of the static scan mode, controls eachof the first antenna elements, the second antenna elements and the thirdantenna elements to emit wideband interrogation signals according to astatic instrument scan cycle having a static instrument scan cycleduration; and in response to receiving a selection of the dynamic scanmode, controls each of the first antenna elements, the second antennaelements and the third antenna elements to emit wideband interrogationsignals according to a dynamic instrument scan cycle having a dynamicinstrument scan cycle duration that is less than the static instrumentscan cycle duration.
 14. The transponder detection device of claim 13wherein, in response to receiving a selection of the static scan mode,the processor controls each of the first antenna elements, the secondantenna elements and the third antenna elements to emit widebandinterrogation signals centered on a first frequency, and furthercontrols each of the first antenna elements, the second antenna elementsand the third antenna elements to emit wideband interrogation signalscentered on a second frequency, the second frequency different from thefirst frequency.
 15. The transponder detection device of claim 11wherein the processor further: determines from a receipt of any of thereturn signals whether any of the resonant tag elements are present inthe work area based at least in part on a frequency of the returnsignals received being within a defined frequency range.
 16. Thetransponder detection device of claim 11 wherein the processor further:determines whether any of the resonant tag elements are present in thework area based at least in part on a Q value of the return signalsreceived.
 17. The transponder detection device of claim 11 wherein theprocessor further: receives electromagnetic signals during a noisedetection portion; determines a noise value indicative of a noise levelthat corresponds to a number of measurements of the electromagneticsignals received during the noise detection portion; adjusts a signaldetection threshold based at least in part on the determined noisevalue; and determines whether any of the resonant tag elements arepresent in the work area based at least in part on a number ofmeasurements of the return signals received and the adjusted signaldetection threshold.
 18. A method to detect surgical objects in a workarea, the surgical objects marked by respective resonant tag elementsthat produce return signals in response to energization, the methodcomprising: providing a transponder detection device that includes ahand-held probe comprising a housing having a cavity therein; a firstcoil assembly and a second coil assembly received within the cavity ofthe housing spaced from each other, wherein each of the first and thesecond coil assemblies respectively includes: a substantiallyspherically shaped coil form that includes three coil support channels,each of the three coil support channels which define an outer coilsupport surface; a first antenna element comprising a first electricalconductor wound around the outer coil support surface of a first one ofthe three coil support channels, the first antenna element arranged totransmit and receive signals generally in a first coordinate direction;a second antenna element comprising a second electrical conductor woundaround the outer coil support surface of a second one of the three coilsupport channels over the first electrical conductor, the second antennaelement arranged to transmit and receive signals generally in a secondcoordinate direction orthogonal to the first coordinate direction; and athird antenna element comprising a third electrical conductor woundaround the outer coil support surface of a third one of the three coilsupport channels over the first electrical conductor and the secondelectrical conductor, the third antenna element arranged to transmit andreceive signals generally in a third coordinate direction orthogonal tothe first coordinate direction and the second coordinate direction;emitting wideband interrogation signals via the respective first antennaelements, the second antenna elements and the third antenna elements ofthe first and the second coil assemblies; receiving any of the returnsignals from any of the resonant tag elements via at least one of therespective first antenna elements, the second antenna elements and thethird antenna elements of the first and the second coil assemblies; anddetermining from a receipt of any of the return signals whether any ofthe resonant tag elements are present in the work area.
 19. The methodof claim 18, further comprising: controlling each of the first antennaelements, the second antenna elements and the third antenna elements toemit wideband interrogation signals in time-wise succession during atransmit portion of respective transmit and receive cycles andcontrolling each of the first antenna elements, the second antennaelements and the third antenna elements to not emit widebandinterrogation signals during a receive portion of respective transmitand receive cycles.
 20. The method of claim 18, further comprising:controlling each of the first antenna elements, the second antennaelements and the third antenna elements to emit wideband interrogationsignals according to a static instrument scan cycle having a staticinstrument scan cycle duration; and controlling each of the firstantenna elements, the second antenna elements and the third antennaelements to emit wideband interrogation signals according to a dynamicinstrument scan cycle having a dynamic instrument scan cycle durationthat is less than the static instrument scan cycle duration.